Synthesis of R-N-methylnaltrexone

ABSTRACT

This invention relates to stereoselective synthesis of R-MNTX and intermediates thereof, pharmaceutical preparations comprising R-MNTX or intermediates thereof and methods for their use.

RELATED APPLICATION

This application claims benefit under 35 U.S.C. 119(e) of the filingdate of U.S. Ser. No. 60/684,616, filed on May 25, 2005, the entiredisclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to stereoselective synthesis of(R)—N-methylnaltrexone (R-MNTX) and intermediates thereof,pharmaceutical preparations comprising R-MNTX or intermediates thereofand methods for their use.

BACKGROUND OF INVENTION

Methylnaltrexone (MNTX) is a quaternary derivative of the pure opioidantagonist, naltrexone. It exists as a salt. Names used for the bromidesalt of MNTX in the literature include: Methylnaltrexone bromide;N-Methylnaltrexone bromide; Naltrexone methobromide; Naltrexone methylbromide; MRZ 2663BR. MNTX was first reported in the mid-70s by Goldberget al as described in U.S. Pat. No. 4,176,186. It is believed thataddition of the methyl group to the ring nitrogen forms a chargedcompound with greater polarity and less liposolubility than naltrexone.This feature of MNTX prevents it from crossing the blood-brain barrierin humans. As a consequence, MNTX exerts its effects in the peripheryrather than in the central nervous system with the advantage that itdoes not counteract the analgesic effects of opioids on the centralnervous system.

MNTX is a chiral molecule and the quaternary nitrogen can be in R or Sconfiguration. (See FIG. 1.) It is unknown whether the differentstereoisomers of MNTX exhibit different biological and chemicalproperties. All of the reported functions of MNTX described in theliterature indicate that MNTX is a peripheral opioid antagonist. Some ofthese antagonist functions are described in U.S. Pat. Nos. 4,176,186,4,719,215, 4,861,781, 5,102,887, 5,972,954, 6,274,591, 6,559,158, and6,608,075, and in U.S. patent application Ser. No. 10/163,482(2003/0022909A1), Ser. No. 10/821,811 (20040266806), Ser. No. 10/821,813(20040259899) and Ser. No. 10/821,809 (20050004155). These uses includereducing the side-effects of opioids without reducing the analgesiceffect of opioids. Such side-effects include nausea, emesis, dysphoria,pruritus, urinary retention, bowel hypomotility, constipation, gastrichypomotility, delayed gastric emptying and immune suppression. The artdiscloses that MNTX not only reduces the side-effects stemming fromopioid analgesic treatment but also reduces the side-effects mediated byendogenous opioids alone or in conjunction with exogenous opioidtreatment. Such side-effects include inhibition of gastrointestinalmotility, post-operative gastrointestinal dysfunction, idiopathicconstipation and other such conditions including, but not limited to,those mentioned above. However, it is unclear from the art whether theMNTX used in these studies was a mixture of R and S stereoisomers or asingle stereoisomer.

The art suggests that isolated stereoisomers of a compound sometimes mayhave contrasting physical and functional properties, although it isunpredictable whether this is the case in any particular circumstance.Dextromethorphan is a cough suppressant, whereas its enantiomer,levomethorphan, is a potent narcotic. R,R-methylphenidate is a drug totreat attention deficit hyperactivity disorder (ADHD), whereas itsenantiomer, S,S-methylphenidate is an antidepressant. S-fluoxetine isactive against migraine, whereas its enantiomer, R-fluoxetine is used totreat depression. The S enantiomer of citalopram is therapeuticallyactive isomer for treatment of depression. The R enantiomer is inactive.The S enantiomer of omeprazole is more potent for the treatment ofheartburn than the R enantiomer.

Bianchetti et al, 1983 Life Science 33 (Sup I):415-418 studied threepairs of diastereoisomers of quaternary narcotic antagonist and theirparent tertiary amines, levallorphan, nalorphine, and naloxone, to seehow the configuration about the chiral nitrogen affected in vitro and invivo activity. It was found that the activity varied considerablydepending on how the quaternary derivatives were prepared. In eachseries, only the diastereomer obtained by methylation of theN-allyl-substituted tertiary amine (referred to as “N-methyldiastereomer”) was potent in displacing ³H-naltrexone from rat brainmembranes, and acting as a morphine antagonist in the guinea-pig ileum.Conversely, diastereoisomers obtained by reacting N-methyl-substitutedtertiary amines with allyl halide (referred to as “N-allyldiastereomers”) did not displace 3H-naltrexone and had negligibleantagonist activity and slight agonist action in the guinea-pig ileum.In vivo findings were generally consistent with those in vitro. Thusonly the “N-methyl” but not the “N-allyl diastereomers” inhibitedmorphine-induced constipation in rats and behaved as antagonists. Theauthor stated that the prepared materials appeared to be pure by ¹H and¹³C nuclear magnetic resonance (NMR) analysis, but these methods are notaccurate. The author cites a literature reference for the assignment ofthe R configuration to the “N-methyl diastereomer” of nalorphine. Noassignment is proposed for the levallorphan and naloxone diastereomers.It would be adventurous to extrapolate the configuration to thesediastereomers (R. J. Kobylecki et al, J. Med. Chem. 25, 1278-1280,1982).

Goldberg et al.'s U.S. Pat. No. 4,176,186, and more recently Cantrell etal.'s WO 2004/043964 A2 describe a protocol for the synthesis of MNTX.Both describe a synthesis of MNTX by quaternizing a tertiaryN-substituted morphinan alkaloid with a methylating agent. Both Goldberget al. and Cantrell et al. are silent as to the stereoisomer(s) producedby the synthesis. The authors remained cautiously silent about thestereochemistry because the stereochemistry could not be determinedbased on prior art. The cyclopropylmethyl side-chain in naltrexone isdifferent from the prior art side-chains and may have affected thestereochemical outcome in the synthesis of MNTX, as may other reactionparameters such as temperature and pressure. Based on the method ofsynthesis described in each, it is unknown whether the MNTX so producedwas R, S or a mixture of both.

S-MNTX in pure form, and a method of making pure S-MNTX have not beendescribed in the literature. Researchers would have been unable todefinitively characterize and distinguish the stereoisomer(s) obtainedby the Goldberg et al. or Cantrell et al. synthesis in the absence ofpure S-MNTX as a standard.

SUMMARY OF THE INVENTION

S-MNTX has now been produced in high purity permitting thecharacterization of its relative retention time in chromatography versusthat of R-MNTX. The pure S-MNTX has been found to have activitydifferent from the activity of MNTX reported in the literature. Thishighlights the need for methods of making and purifying R-MNTX to highpurity.

The present invention provides substantially pure R-MNTX andintermediates thereof, crystals of substantially pure R-MNTX andintermediates thereof, novel methods for making substantially pureR-MNTX, methods for analyzing and quantifying R-MNTX in a mixture ofR-MNTX and S-MNTX, methods of isolating R-MNTX from a mixture of R-MNTXand S-MNTX, pharmaceutical products containing the same and related usesof these materials.

The invention provides synthetic routes for stereoselective synthesis ofR-MNTX, substantially pure R-MNTX, crystals of substantially pureR-MNTX, pharmaceutical preparations containing substantially pureR-MNTX, and methods for their use.

According to one aspect of the invention, a composition is provided thatcomprises MNTX in R configuration with respect to nitrogen present atgreater than 99.5%. In other embodiments the MNTX in R configurationwith respect to nitrogen is present in the composition in greater thanabout 99.6%, or about 99.7%, or about 99.8%, or about 99.9%, or about99.95%, or even more preferably greater than 99.95%. In one embodiment,there is no detectable S-MNTX using the chromatographic proceduresdescribed herein. Preferably, the composition is free of HPLC detectableS-MNTX. In one embodiment there is no HPLC detectable S-MNTX at adetection limit of 0.02% and a quantitation limit of 0.05%. In yetanother embodiment the composition of the invention contains 99.85% ofthe MNTX is in R configuration with respect to nitrogen and it containsHPLC detectable S-MNTX at a detection limit of 0.02% and a quantitationlimit of 0.05%.

According to one aspect of the invention a composition is provided thatcomprises MNTX, wherein at least 99.6%, 99.7%, 99.8%, 99.85%, 99.9%, andeven 99.95% of the MNTX in the composition is in the R configurationwith respect to nitrogen, and one or more of a buffering agent, achelating agent, a preserving agent, a cryoprotecting agent, alubricating agent, a preservative, an anti-oxidant, or a binding agent.

R-MNTX is a salt. Therefore there will be a counterion, which for thepresent application, includes the zwitterion. Typically, the counteriona halide, sulfate, phosphate, nitrate or an anionic-charged organicspecies. Halides include bromide, iodide, chloride, and fluoride. Incertain embodiments the halide is iodide and in other importantembodiments the halide is bromide. In certain embodiments, theanionic-charged organic species is a sulfonate or a carboxylate.Examples of sulfonates include mesylate, besylate, tosylate, andtriflate. Examples of carboxylates include formate, acetate, citrate,and fumarate.

According to another aspect of the invention, the foregoing compositionsthat comprise MNTX in R configuration with respect to nitrogen in someimportant embodiments is a crystal, a solution, or a bromide salt ofMNTX. In other embodiments, the foregoing compositions arepharmaceutical preparations, preferably in effective amounts and with apharmaceutically acceptable carrier.

According to one aspect of the invention, a crystal of MNTX is providedthat is at least about 99.5%, or about 99.6% or about 99.7%, or is about99.8%, or about 99.9%, or most preferably greater than 99.95% of MNTX inR configuration with respect to nitrogen.

According to one aspect of the invention, there is provided a compoundof the formula:

wherein R is a hydroxyl protecting group. The hydroxyl protecting groupcan be any of numerous such groups. In important embodiments it isselected from the group consisting of: isobutyryl, 2-methyl butyryl,tertbutyl carbonyl, silyl ethers, 2-tetrahydropyranyl ethers, and alkylcarbonates. Most preferably the hydroxyl protecting group is isobutyryl.

According to one aspect of the invention there is provided a compound ofthe formula:

wherein R is a hydroxyl protecting group. The hydroxyl protecting groupis selected from the group consisting of: isobutyryl, 2-methyl butyryl,tertbutyl carbonyl, silyl ethers, 2-tetrahydropyranyl ethers, and alkylcarbonates. Most preferably the hydroxyl protecting group is isobutyryl.The compound in one embodiment is isolated. By isolated it is meant thecompound is at least 50% pure. The compound can be obtained at levels ofeven greater purity, such as 60%, 70%, 80%, 90%, or even greater than95% purity. In other embodiments the compound is in R configuration withrespect to nitrogen, the R form being present in greater than 50%, 60%,70%, 80%, 90%, 95%, 99%, or even 99.5% % versus the S form.

According to another aspect of the invention, a method forstereoselective synthesis of R-MNTX is provided. This method involvesadding a hydroxyl protecting group to naltrexone to yield3-O-protected-naltrexone; methylating the 3-O-protected-naltrexone toyield 3-O-protected-R-MNTX salt; and removing hydroxyl protecting groupto yield R-MNTX. In some embodiments of the invention the hydroxylprotecting group can be added in the presence of each or both: anorganic solvent and/or a tertiary amine that is not naltrexone. In someembodiments of the invention the naltrexone is methylated by reactingthe 3-O-protected-naltrexone with methyl iodide to produce3-O-protected-R-MNTX iodide salt. The 3-O-protected-naltrexone can beprotected in important embodiments by a hydroxyl protecting group suchas isobutyryl. In a preferred embodiment of the invention, the3-O-protected-R-MNTX iodide salt is treated with hydrobromic acid toremove the protecting group and produce R-MNTX bromide/iodide salt, andthe bromide/iodide salt is passed through an anion exchange resin column(bromide form) to yield R-MNTX bromide. In any of the foregoing aspectsof the invention the tertiary amine that is not MNTX can betriethylamine. In any of the foregoing aspects of the invention theorganic solvent can be tetrahydrofuran. In any of the foregoing aspectsof the invention the hydroxyl protecting group can be isobutyryl.

According to another aspect of the invention a method for isolation andpurification of R-MNTX is provided, comprising passing the crude R-MNTXthrough a chromatography column and collecting the R-MNTX which elutesat the R-MNTX retention time. This process can be in addition to themethod described above, after the deprotecting step and/or the anionexchange resin column step.

According to another aspect of the invention a method for analyzingR-MNTX in a mixture of R-MNTX and S-MNTX is provided. The methodinvolves conducting high performance liquid chromatography (HPLC) andapplying R-MNTX to the chromatography column as a standard. The methodpreferably involves applying both S-MNTX and R-MNTX as standards todetermine relative retention/elution times. Relative retention times ofR and S are described herein.

Pure S-MNTX can be obtained according to the following procedure: S-MNTXsalt can be synthesized by combining iodomethylcyclopropane or anothercyclopropylmethyl derivative with oxymorphone in a dipolar aproticsolvent. The cyclopropylmethyl derivative contains a leaving group,preferably a halide, such as iodine or sulfonate. The dipolar aproticsolvent may be: N-methylpyrrolidone (NMP), dimethyl formamide,methylphosphoramide, acetone, 1,4-dioxane, acetonitrile, or combinationsthereof. The synthesized S-MNTX can be purified by chromatography,recrystallization, multiple recrystallizations, or a combinationthereof. The reaction can be carried out under atmospheric conditionsacross a wide temperature spectrum, for example, at 70° C., or under acontrolled reaction temperature between 65° C. to 75° C. Counterions maybe substituted, optionally, for iodide by transferring the S-MNTX iodosalt to a second solvent, such as isopropyl acetate or dioxane andexchanging iodide for a counterion other than iodide. Examples ofcounterions are bromide, chloride, fluoride, nitrate, sulfonate, orcarboxylate. The sulfonate can be mesylate, besylate, tosylate ortriflate. The carboxylate can be formate, acetate, citrate and fumarate.The reaction in the second solvent can be conducted at room temperature.

In one aspect of this invention, the chromatography is conducted usingtwo solvents, solvent A and solvent B, wherein solvent A is an aqueoussolvent and solvent B is a methanolic solvent and wherein both A and Bcontain trifluoroacetic acid (TFA). Preferably, A is 0.1% aqueous TFAand B is 0.1% methanolic TFA. In important embodiments the columncomprises a bonded, end-capped silica. In important embodiments, thepore size of the column gel is 5 microns. In a most preferredembodiment, the column, flow rate and gradient program are as follows:

-   Column: Luna C18(2), 150×4.6 mm, 5μ-   Flow Rate: 1 mL/min-   Gradient Program:

Time (min) % A % B  0:00 95 5  8:00 65 35 12:00 35 65 15:00 0 100 16:0095 5 18:00 95 5

Detection can be carried out conveniently by ultraviolet (UV) wavelength@ 230 nm. Quantitation Limit is the lowest amount of S-MNTX that can beconsistently measured and reported, regardless of variations inlaboratories, analysts, instruments or reagent lots. Detection Limit isthe lowest amount of S-MNTX in a sample which can be detected but notnecessarily quantitated as an exact value.

The foregoing HPLC also can be used to determine the relative amount ofS-MNTX and R-MNTX and the intermediates of the synthesis thereof bydetermining the area under the respective R and S curves in thechromatogram produced. According to another aspect of the invention amethod for isolation and purification of R-MNTX and the3-0-protected-R-MNTX salt intermediate is provided, comprisingrecrystallizing the crude R-MNTX or intermediates thereof from a solventor a mixture of solvents. This process can be in addition to the methoddescribed above, after the deprotection step and/or the anion exchangeresin column step.

According to another aspect of the invention, a method is provided forstereoselective synthesis of 3-O-protected R-MNTX salt comprisingmethylating a 3-O-protected-naltrexone with a methylating agent to yield3-O-protected-R-MNTX salt. The hydroxyl protecting group of the3-O-protected-naltrexone in certain embodiments is isobutyryl, 2-methylbutyryl, tertbutyl carbonyl, silyl ethers, 2-tetrahydropyranyl ethers,and alkyl carbonates. The 3-O-protected R-MNTX is a salt with an anionthat can be, for example, a halide, sulfate, phosphate, nitrate or anorganic anionic-charged species. The halide is bromide, iodide,chloride, or fluoride. The organic anionic-charged species can be, forexample, a sulfonate or carboxylate. Exemplary sulfonates are mesylate,besylate, tosylate, or triflate. Exemplary carboxylates are formate,acetate, citrate, or fumarate. The method can further involve exchangingthe anion with a different anion. The methylating agent can be a methylgroup susceptible to nucleophilic attack, and a leaving group. Exemplarymethylating agents are selected from the group consisting of methylhalide, dimethyl sulfate, methyl nitrate and methyl sulfonate. Methylhalides are methyl iodide, methyl bromide, methyl chloride and methylfluoride. Methyl sulfonates include methyl mesylate, methyl besylate,methyl tosylate, and methyl triflate. In one embodiment, the methylationis conducted at a temperature range from about >70° C. to about 100° C.,or from 80° C. to about 90° C., or preferably at about 88° C. Themethylation reaction is conducted for about 1 hour to 24 hours, or about5 hour to 16 hours and in one embodiment for about 10 hours. The methodcan further involve purification of the 3-O-protected R-MNTX salt usingat least one purification technique, such as chromatography orrecrystallization. The chromatography can be reverse-phasechromatography or regular phase chromatography. In some embodiments, theregular phase chromatography can use alumina or silica gel. The3-O-protected-naltrexone can be purified prior to methylation.

According to one aspect of the invention a pharmaceutical composition isprovided that comprises R-MNTX free of detectable S-MNTX by thechromatography procedures described herein or the 3-0-protected-R-MNTXsalt intermediate and a pharmaceutically acceptable carrier. In oneembodiment the pharmaceutical composition is a packaged unit dosage or amulti-unit dosage. In yet another embodiment the packaged unit dosage isa solution. The pharmaceutical composition in one embodiment is asolution. In another embodiment it is an enteric coated solid dosageform. In still another embodiment it is a sustained release formulation.According to yet another aspect of the invention, a pharmaceuticalpreparation containing R-MNTX or the 3-0-protected-R-MNTX saltintermediate in a lyophilized formulation is prepared by combining acryoprotective agent, such as mannitol, with the R-MNTX formulation. Thelyophilized preparation may also contain any one of, any combination of,or all of a buffering agent, an antioxidant, an isotonicity agent and anopioid. In some embodiment the aforementioned pharmaceutical compositioncan further comprise one pharmaceutical agent that is not an opioidantagonist. In one embodiment of the invention the aforementionedpharmaceutical composition can comprise a pharmaceutical agent that isan opioid. In yet another embodiment, the pharmaceutical composition canfurther comprise at least one opioid, and at least one pharmaceuticalagent that is not an opioid or an opioid antagonist. In a preferredembodiment the pharmaceutical agent that is not an opioid or an opioidantagonist is an antiviral agent, an anti-infective agent, an anticanceragent, an antispasmodic agent, an anti-muscarinic agent, a steriodal ornon-steriodal anti-inflammatory agent, a pro-motility agent, a 5HT₁agonist, a 5HT₃ antagonist, a 5HT₄ antagonist, a 5HT₄ agonist, a bilesalt sequestering agent, a bulk-forming agent, an alpha2-adrenergicagonist, a mineral oil, an antidepressant, a herbal medicine, ananti-diarrheal medication, a laxative, a stool softener, a fiber or ahematopoietic stimulating agent.

The pharmaceutical compositions of the invention can be provided inkits. The kits are a package containing a sealed container comprisingthe pharmaceutical preparations of the present invention andinstructions for use. The kits contain R-MNTX that is free of HPLCdetectable S-MNTX. The kit in one embodiment contains 40 mg/mL R-MNTX.The kit in another embodiment contains 30 mg/mL of R-MNTX. The kit canfurther include an opioid or opioid agonist, or it can include at leastone pharmaceutical agent that is not an opioid or an opioid antagonist.In one embodiment, the kit is a package containing a sealed containercomprising the pharmaceutical preparation that is or the3-0-protected-R-MNTX salt and instructions for use. The kit in oneembodiment contains 40 mg/mL 3-0-protected-R-MNTX salt. The kit inanother embodiment contains 30 mg/mL of 3-0-protected-R-MNTX salt. Thekit can further include an opioid or opioid agonist, or it can includeat least one pharmaceutical agent that is not an opioid or an opioidantagonist.

According to another aspect of the invention, methods are provided forensuring the manufacture of R-MNTX (which is an opioid antagonist) thatis free of S-MNTX (which is an opioid agonist). The methods permit forthe first time the assurance that a pharmaceutical preparation of R-MNTXwhich is intended for antagonist activity is not contaminated with acompound that opposes the activity of R-MNTX. This is particularlydesirable when R-MNTX is administered to oppose the side effects ofopioid therapy, as opioids appear to act synergistically with S-MNTX tooppose the activity of R-MNTX. In this aspect of the invention, a methodis provided for manufacturing R-MNTX. The method involves:

(a) obtaining a first composition containing R-MNTX, (b) purifying thefirst composition by chromatography, recrystallization or a combinationthereof, (c) conducting HPLC on a sample of purified first compositionusing S-MNTX as a standard, and (d) determining the presence or absenceof S-MNTX in the sample. In an important embodiment, both R-MNTX andS-MNTX are used as standards, to determine for example relativeretention time of R-MNTX and S-MNTX. In one embodiment, the purifying ismultiple recryallization steps or multiple chromatography steps. Inanother embodiment, the purifying is carried out until S-MNTX is absentfrom the sample as determined by HPLC. It should be understood, however,that the purified first composition in some aspects of the invention isnot necessarily free of detectable S-MNTX. The presence of such S-MNTX,for example, might indicate that further purification steps should beconducted if purer R-MNTX is desired. The methods can further involvepackaging purified first composition that is free of HPLC detectableS-MNTX. The methods further can include providing indicia on or withinthe packaged, purified first composition indicating that the packaged,purified first composition is free of HPLC detectable S-MNTX. The methodfurther can involve packaging a pharmaceutically effective amount fortreating anyone of the conditions described herein. The firstcomposition containing R- and S-MNTX can be obtained by the methodsdescribed herein.

According to one aspect of the invention, the purifying is carried outuntil S-MNTX is less than 0.4%, 0.3%, 0.2%, 0.15%, 0.1%, 0.05%, even isabsent from the purified first composition as determined by HPLC with adetection limit of 0.02 and a quanitiation limit of 0.05%. In oneembodiment the method provides indicia on or with the packaged purifiedfirst composition indicating a level of S-MNTX in the packaged firstpurified composition.

According to one aspect of the invention a package is provided thatcontains a composition comprising R-MNTX and indicia on or containedwithin the package indicating a level of S-MNTX in the composition. Inone embodiment the level of S-MNTX is less than 0.4%, 0.3%, 0.2%, 0.15%,0.1%, 0.05%, or is absent from the sample. In yet another embodiment,the package further contains, mixed together with the R-MNTX, one ormore of a buffering agent, a chelating agent, a preserving agent, acryoprotecting agent, a lubricating agent, a preservative, ananti-oxidant, or a binding agent.

According to one aspect of the invention a method of preparing apharmaceutical product in provided, by selecting a composition of R-MNTXbecause it contains S-MNTX at a level that is less than 0.4%, 0.3%,0.2%, 0.15%, 0.1%, 0.05% of, or is absent from the composition, andformulating the composition into a unit or multi unit dosage foradministration to a patient.

According to another aspect of the invention, a packaged product isprovided. The package contains a composition comprising R-MNTX, whereinthe composition is free of HPLC detectable S-MNTX, and indicia on orcontained within the package indicating that the composition is free ofdetectable S-MNTX. The composition can take on a variety of forms,including, but not limited to, a standard for use in laboratoryexperiments, a standard for use in manufacturing protocols, or apharmaceutical composition. If the composition is a pharmaceuticalcomposition, then one important form of indicia is writing on a label orpackage insert describing the characteristics of the pharmaceuticalpreparation. The indicia can indicate directly that the composition isfree of S-MNTX, or it can indicate the same indirectly, by stating forexample that the composition is pure or 100% R-MNTX. The pharmaceuticalcomposition can be for treating any of the conditions described herein.The pharmaceutical composition can contain an effective amount of thepure R-MNTX and can take any of the forms described below as ifspecifically recited in this summary, including, but not limited to,solutions, solids, semi-solids, enteric coated materials and the like.

According to one aspect of the invention, a method is provided fortreating or preventing opioid-induced side effects comprisingadministering to a patient the R-MNTX free of detectable S-MNTX by thechromatography procedures described herein or the 3-O-protected-R-MNTXsalt intermediate composition of any of the foregoing aspects of theinvention in an amount effective to treat the opioid-induced sideeffect. In one embodiment of the invention the patient is chronicallyadministered opioids. In another embodiment the patient is acutelyadministered opioids. The opioid-induced side effect is preferablyselected from a group consisting of constipation, immune suppression,inhibition of gastrointestinal motility, inhibition of gastric emptying,nausea, emesis, incomplete evacuation, bloating, abdominal distension,increased gastroesophageal reflux, hypotension, bradycardia,gastrointestinal dysfunction, pruritus, dysphoria, and urinaryretention. In one preferred embodiment the opioid-induced side effect isconstipation. In another preferred embodiment the opioid-induced sideeffect is inhibition of gastrointestinal motility or inhibition ofgastric emptying. In yet another preferred embodiment the opioid-inducedside effect is nausea or emesis. In yet another preferred embodiment theopioid-induced side effect is pruritus. In yet another preferredembodiment the opioid-induced side effect is dysphoria. In yet anotherpreferred embodiment the opioid-induced side effect is urinaryretention.

According to one aspect of the invention, a method is provided fortreating a patient receiving an opioid for pain resulting from surgerycomprising administering to the patient an R-MNTX composition free ofdetectable S-MNTX by the chromatography procedures described herein orthe 3-O-protected-R-MNTX salt intermediate in an amount effective topromote gastrointestinal motility, gastric emptying or relief ofconstipation.

According to another aspect of the invention, a method is provided forinducing laxation in a patient in need of Taxation, comprisingadministering to the patient an R-MNTX composition free of detectableS-MNTX by the chromatography procedures described herein or the3-O-protected-R-MNTX salt intermediate in an effective amount.

According to yet another aspect of the invention, a method is providedfor preventing and/or treating impaction in a patient in need of suchprevention/treatment, comprising administering to the patient an R-MNTXcomposition free of detectable S-MNTX by the chromatography proceduresdescribed herein or the 3-O-protected-R-MNTX salt intermediate in aneffective amount.

According to yet another aspect of the invention, a method is providedfor preventing and/or treating post-operative bowel dysfunctionfollowing surgery, in particular abdominal surgery in a patient in needof such prevention/treatment, comprising administering to the patient anR-MNTX composition free of detectable S-MNTX by the chromatographyprocedures described herein or the 3-O-protected-R-MNTX saltintermediate in an effective amount.

According to one aspect of the invention, a method is provided fortreating or preventing endogenous opioid-induced gastrointestinaldysfunction comprising administering to the patient an R-MNTXcomposition free of detectable S-MNTX by the chromatography proceduresdescribed herein or the 3-O-protected-R-MNTX salt intermediate in anamount effective to treat the endogenous opioid-induced gastrointestinaldysfunction. The gastrointestinal dysfunction can be selected from agroup consisting of inhibition of gastrointestinal motility,constipation and ileus. In some embodiments of the invention the ileusis selected from the group comprising of: post-operative ileus,post-partum ileus, paralytic ileus.

According to one aspect of the invention, a method is provided forpreventing or treating idiopathic constipation comprising administeringto the patient an R-MNTX composition free of detectable S-MNTX by thechromatography procedures described herein or the 3-O-protected-R-MNTXsalt intermediate in an amount effective to prevent or treat theidiopathic constipation.

According to yet another aspect of the invention, a method is providedfor treating irritable bowel syndrome comprising administering to thepatient an R-MNTX composition free of detectable S-MNTX by thechromatography procedures described herein or the 3-O-protected-R-MNTXsalt intermediate in an amount effective to ameliorate at least onesymptom of the irritable bowel syndrome. In some embodiments of theinvention the R-MNTX composition or the 3-O-protected-R-MNTX saltcomposition further comprises at least one irritable bowel syndrometherapeutic agent. The irritable bowel syndrome therapeutic agent can beselected from the groups consisting of antispasmodics, anti-muscarinics,anti-inflammatory agents, pro-motility agents, 5HT₁ agonists, 5HT₃antagonists, 5HT₄ antagonists, 5HT₄ agonists, bile salt sequesteringagents, bulk-forming agents, alpha2-adrenergic agonists, mineral oils,antidepressants, herbal medicines, anti-diarrheal medication andcombinations thereof.

According to one aspect of the invention methods are provided forparenteral administration of the compounds and compositions of theinvention including but not limited to intravenous, intramuscular andsubcutaneous administration. In one embodiment of the invention thecompounds of the invention are in pharmaceutical preparations suitablefor use in pre-filled syringes, pre-filled pen injectors, cartridges foruse in pen injectors, reusable syringes or other medical injectors,liquid dry injectors, needleless pen systems, syrettes, autoinjectors,or other patient-controlled injection devices.

These and other aspects of the invention are described in greater detailherein.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 provides the chemical structure of bromide salts of R-MNTX andS-MNTX.

FIG. 2 is a chromatogram showing the separation of R and S forms of MNTXin a mixture of S- and R-MNTX.

FIG. 3 is a chromatogram of R-MNTX with the addition of approximately0.1% of the S-MNTX isomer.

FIG. 4 is a chromatogram of R-MNTX with the addition of approximately1.0% of the S-MNTX isomer.

FIG. 5 is a chromatogram of R-MNTX with the addition of approximately3.0% of the S-MNTX isomer.

FIG. 6 shows a reaction scheme for the synthesis of R-MNTX using apreferred hydroxyl protecting group.

FIG. 7 shows an alternative reaction scheme for the synthesis of R-MNTXusing a preferred hydroxyl protecting group.

FIG. 8 shows a kit according to the invention.

DETAILED DESCRIPTION

The invention provides synthetic routes for stereoselective synthesis ofR-MNTX, [morphinanium,17R,17-(cyclopropylmethyl)-4,5-epoxy-3,14-dihydroxy-17-methyl-6-oxo-,salt, (5α)-(9Cl)], substantially pure R-MNTX, crystals of substantiallypure R-MNTX, pharmaceutical preparations containing substantially pureR-MNTX, and methods for their use.

R-MNTX has the structure in the formula:

wherein X⁻ is a counterion. The counterion can be any counter ion,including a zwitterion. Preferably the counterion is pharmaceuticallyacceptable. Counterions include halides, sulfates, phosphates, nitrates,and anionic-charged organic species. The halide can be iodide, bromide,chloride, fluoride or a combination thereof. In one embodiment thehalide is iodide. In a preferred embodiment the halide is bromide. Theanionic-charged organic species may be a sulfonate or carboxylate. Thesulfonate may be mesylate, besylate, tosylate, or triflate. Thecarboxylate may be formate, acetate, citrate, or fumarate.

The invention further provides an R-MNTX intermediate, isolated3-O-protected-R-MNTX salt of the formula:

wherein R is a hydroxyl protecting group, substantially pure3-O-protected-R-MNTX salt, crystals of substantially pure3-O-protected-R-MNTX salt, pharmaceutical preparations containingsubstantially pure 3-O-protected-R-MNTX salt, and methods for their use.The invention further provides synthetic routes for stereoselectivesynthesis of 3-O-protected-R-MNTX salt.

“Alkyl”, in general, refers to an aliphatic hydrocarbon group which maybe straight, branched or cyclic having from 1 to about 10 carbon atomsin the chain, and all combinations and subcombinations of rangestherein. “Branched” refers to an alkyl group in which a lower alkylgroup, such as methyl, ethyl or propyl, is attached to a linear alkylchain. In certain preferred embodiments, the alkyl group is a C₁-C₅alkyl group, i.e., a branched or linear alkyl group having from 1 toabout 5 carbons. In other preferred embodiments, the alkyl group is aC₁-C₃ alkyl group, i.e., a branched or linear alkyl group having from 1to about 3 carbons. Exemplary alkyl groups include methyl, ethyl,n-propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl,hexyl, heptyl, octyl, nonyl and decyl. “Lower alkyl” refers to an alkylgroup having 1 to about 6 carbon atoms. Preferred alkyl groups includethe lower alkyl groups of 1 to about 3 carbons.

An “alkylating agent” is a compound that can be reacted with a startingmaterial to bind, typically covalently, an alkyl group to the startingmaterial. The alkylating agent typically includes a leaving group thatis separated from the alkyl group at the time of attachment to thestarting material. Leaving groups may be, for example, halogens,halogenated sulfonates or halogenated acetates. An example of analkylating agent is cyclopropylmethyl iodide.

“Methylating agent” means a reactive species, having electrophilicproperties, that is capable of introducing a “methyl group” at thenitrogen atom of naltrexone, so as to form a covalent bond therewith.Illustrative methylating agents can be represented by the formula CH₃Z,wherein “Z” is a leaving group which, upon its departure, enables CH₃ toform a covalent bond with the nitrogen atom of naltrexone, forming MNTX.Methylating agents in general, and leaving groups in general, are wellknown to those of ordinary skill in the art and are describedextensively in both the patent literature and in chemistry text books.Suitable Z groups include, but are not limited to, fluoro, chloro,bromo, iodo, —OSO₂CF₃, CH₃OSO₂O—, —OSO₂CH₃, —OSO₂C₆H₄-p-CH₃,—OSO₂C₆H₄-p-Br.

“Alkenyl”, in general, refers to an alkyl group containing at least onecarbon-carbon double bond and having from 2 to about 10 carbon atoms inthe chain, and all combinations and subcombinations of ranges therein.In certain preferred embodiments, the alkenyl group is a C₂-C₁₀ alkylgroup, i.e., a branched or linear alkenyl group having from 2 to about10 carbons. In other preferred embodiments, the alkenyl group is a C₂-C₆alkenyl group, i.e., a branched or linear alkenyl group having from 2 toabout 6 carbons. In still other preferred embodiments, the alkenyl groupis a C₃-C₁₀ alkenyl group, i.e., a branched or linear alkenyl grouphaving from about 3 to about 10 carbons. In yet other preferredembodiments, the alkenyl group is a C₂-C₅ alkenyl group, i.e., abranched or linear alkenyl group having from 2 to about 5 carbons.Exemplary alkenyl groups include, for example, vinyl, propenyl, butenyl,pentenyl, hexenyl, heptenyl, octenyl, nonenyl and decenyl groups.

“Alkylene”, in general, refers to a straight or branched bivalentaliphatic hydrocarbon group having from 1 to about 6 carbon atoms, andall combinations and subcombinations of ranges therein. The alkylenegroup may be straight, branched or cyclic. Exemplary alkylene groupsinclude, for example, methylene (—CH₂—), ethylene (—CH₂—CH₂—) andpropylene (—(CH₂)₃—). There may be optionally inserted along thealkylene group one or more oxygen, sulfur or optionally substitutednitrogen atoms, wherein the nitrogen substituent is alkyl as describedpreviously. Preferred alkylene groups have from about 1 to about 4carbons.

“Alkenylene”, in general, refers to an alkylene group containing atleast one carbon—carbon double bond. Exemplary alkenylene groupsinclude, for example, ethenylene (—CH═CH—) and propenylene (—CH═CHCH₂—).Preferred alkenylene groups have from 2 to about 4 carbons.

“Cycloalkyl”, in general, refers to any stable monocyclic or bicyclicring having from about 3 to about 10 carbons, and all combinations andsubcombinations of ranges therein. In preferred embodiments, thecycloalkyl group is a C₃-C₈ cycloalkyl group, i.e., a cycloalkyl grouphaving from about 3 to about 8 carbons, with C₃-C₆ cycloalkyl groups,i.e., cycloalkyl groups having from about 3 to about 6 carbons beingmore preferred. The cycloalkyl group may be optionally substituted withone or more cycloalkyl group substituents. Preferred cycloalkyl groupsubstituents include alkyl, preferably C₁-C₃ alkyl, alkoxy, preferablyC₁-C₃ alkoxy, or halo. Exemplary cycloalkyl groups include, for example,cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl andcyclooctyl groups.

“Cycloalkyl-substituted alkyl”, in general, refers to a linear alkylgroup, preferably a lower alkyl group, substituted at a terminal carbonwith a cycloalkyl group, preferably a C₃-C₈ cycloalkyl group. Typicalcycloalkyl-substituted alkyl groups include cyclohexylmethyl,cyclohexylethyl, cyclopentylethyl, cyclopentylpropyl, cyclopropylmethyland the like.

“Cycloalkenyl”, in general, refers to an olefinically unsaturatedcycloalkyl group having from about 4 to about 10 carbons, and allcombinations and subcombinations of ranges therein. In preferredembodiments, the cycloalkenyl group is a C₅-C₈ cycloalkenyl group, i.e.,a cycloalkenyl group having from about 5 to about 8 carbons.

“Alkoxy”, in general, refers to an alkyl-O— group where alkyl is aspreviously described. Exemplary alkoxy groups include, for example,methoxy, ethoxy, propoxy, butoxy and heptoxy.

“Alkoxy-alkyl”, in general, refers to an alkyl-O-alkyl group where alkylis as previously described.

“Acyl”, in general, means an alkyl-CO— group wherein alkyl is aspreviously described. Preferred acyl groups comprise lower alkyl groups,such as alkyl of about 1 to about 3 carbons. Exemplary acyl groupsinclude acetyl, propanoyl, 2-methylpropanoyl, and butanoyl.

“Aryl”, in general, refers to an aromatic carbocyclic radical containing6, 10 or 14 carbons. The phenyl group may be optionally substituted withone or two or more substituents. Preferred aryl group substituentsinclude alkyl groups, preferably C₁-C₅ alkyl groups. Exemplary arylgroups include phenyl and naphthyl.

“Aryl-substituted alkyl”, in general, refers to an linear alkyl group,preferably a lower alkyl group, substituted at a carbon with anoptionally substituted aryl group, preferably an optionally substitutedphenyl ring. Exemplary aryl-substituted alkyl groups include, forexample, phenylmethyl, phenylethyl and 3-(4-methylphenyl)propyl.

“Heterocyclic”, in general, refers to a monocyclic or multicylic ringsystem radical containing from about 4 to about 10 members, and allcombinations and subcombinations of ranges therein, wherein one or moreof the members is an element other than carbon, for example, nitrogen,oxygen or sulfur. The heterocyclic group may be aromatic or nonaromatic.Exemplary heterocyclic groups include, for example, isoxazole, pyrroleand piperidine groups.

“Organic solvent” has its common ordinary meaning to those of skill inthis art. Exemplary organic solvents useful in the invention include,but are not limited to tetrahydrofuran, acetone, hexane, ether,chloroform, acetic acid, acetonitrile, chloroform, cyclohexane,methanol, and toluene. Anhydrous organic solvents are included.

“Dipolar aprotic” solvents are protophilic solvents that cannot donatelabile hydrogen atoms and that exhibit a permanent dipole moment.Examples include acetone, ethyl acetate, dimethyl sulfoxide (DMSO),dimethyl formamide (DMF) and N-methylpyrrolidone.

“Dipolar protic” solvents are those that can donate labile hydrogenatoms and that exhibit a permanent dipole moment. Examples includewater, alcohols such as 2-propanol, ethanol, methanol, carboxylic acidssuch as formic acid, acetic acid, and propionic acid.

“Tertiary amines” has its common, ordinary meaning. In general, thetertiary amines useful in the invention have the general formula:

wherein R₁, R₂, and R₃ are identical or a combination of differentstraight or branched chain alkyl groups, alkenyl groups, alkylenegroups, alkenylene groups, cycloalkyl groups, cycloalkyl-substitutedalkyl groups, cycloalkenyl groups, alkoxy groups, alkoxy-alkyl groups,acyl groups, aryl groups, aryl-substituted alkyl groups, andheterocyclic groups. Exemplary tertiary amines useful according to theinvention are those where R₁₋₃ is an alkyl group of the formula(C_(n)H_(2n+1), n=1-4), or aralkyl group of the formula (C₆H₅ (CH₂)_(n)—[n=1-2]. Exemplary tertiary amines useful according to the inventionalso are cycloalkyl tertiary amines (e.g., N-methylmorpholine,N-methylpyrrolidine, N-methylpiperidine), pyridine and Proton Sponge®(N,N,N′,N′-tetramethyl-1,8-naphthalene).

As will be readily understood, functional groups present may containprotecting groups during the course of synthesis. Protecting groups areknown per se as chemical functional groups that can be selectivelyappended to and removed from functionalities, such as hydroxyl groupsand carboxyl groups. These groups are present in a chemical compound torender such functionality inert to chemical reaction conditions to whichthe compound is exposed. Any of a variety of protecting groups may beemployed with the present invention. Preferred protecting groups arethose that are stable during formation, isolation and purification. Apreferred protecting group is an isobutyryl groups,); silyl ethers(SiR₃, wherein each R can be independently C₁-C₆ alkyl, straight chainor branched); 2-tetrahydropyranyl ether, alkyl carbonates; abenzyloxycarbonyl group and a tert-butyloxycarbonyl group. Otherpreferred protecting groups that may be employed in accordance with thepresent invention are described in Greene, T. W. and Wuts, P. G. M.,Protective Groups in Organic Synthesis 2d. Ed., Wiley & Sons, 1991. Theexpression “hydroxyl protective group” as used hereinbelow is intendedto designate a group which is inserted in place of the hydrogen atom ofan OH group.

When the hydroxyl protective group is an aliphatic ester it preferablyrepresents an radical selected from the group consisting of alkanoylhaving 3 to 8 carbon atoms; alkenoyl having one or two double bonds and3 to 8 carbon atoms;

wherein the cycloalkyl portion contains 3 to 7 ring atoms and r is zero,one, two or three; phenoxyacetyl; pyridinecarbonyl; and

wherein r is zero, one, two or three and phenyl is unsubstituted or issubstituted by 1 to 3 alkyl groups each having 1 to 4 carbon atoms,alkoxy having 1 to 4 carbon atoms, halo, trifluoromethyl, dialkylaminohaving 2 to 8 carbon atoms or alkanoylamino having 2 to 6 carbon atoms.

When the acyl group is alkanoyl, there are included both unbranched andbranched alkanoyl, for example, propionyl, butyryl, isobutyryl, valeryl,isovaleryl, 2-methylbutanoyl, pivalyl (pivaloyl), 3-methylpentanoyl,3,3-dimethylbutanoyl, 2,2-dimethylpentanoyl and the like. Pivalyl,isobutyryl and isovaleryl are important examples.

When the acyl group is alkenoyl, there are included, for example,crotonyl, 2,5-hexadienoyl and 3,6-octadienoyl.

When the acyl group is

there are included cycloalkanecarbonyl and cycloalkanealkanoyl groupswherein the cycloalkane portion can optionally bear 1 or 2 alkyl groupsas substituents, e.g. cyclopropanecarbonyl,1-methylcyclopropanecarbonyl, cyclopropaneacetyl,α-methylcyclopropaneacetyl, 1-methylcyclopropaneacetyl,cyclopropanepropionyl, α-methylcyclopropanepropionyl,2-isobutylcyclopropanepropionyl, cyclobutanecarbonyl,3,3-dimethylcyclobutanecarbonyl, cyclobutaneacetyl,2,2-dimethyl-3-ethylcyclobutaneacetyl, cyclopentanecarbonyl,cyclohexaneacetyl, cyclohexanecarbonyl, cycloheptanecarbonyl andcycloheptanepropionyl. Cyclohexanecarbonyl is especially preferred.

When the acyl group is pyridinecarbonyl, there are included picolinoyl(2-pyridinecarbonyl), nicotinoyl (3-pyridinecarbonyl) and isonicotinoyl(4-pyridinecarbonyl).

When the acyl group is

there are included, for example, benzoyl, phenylacetyl,α-phenylpropionyl, β-phenylpropionyl, p-toluyl, m-toluyl, o-toluyl,o-ethylbenzoyl, p-tert-butylbenzoyl, 3,4-dimethylbenzoyl,2-methyl-4-ethylbenzoyl, 2,4,6-trimethylbenzoyl, m-methylphenylacetyl,p-isobutylphenylacetyl, β-(p-ethylphenyl)propionyl, p-anisoyl,m-anisoyl, o-anisoyl, m-isopropoxybenzoyl, p-methoxyphenylacetyl,m-isobutoxyphenylacetyl, m-diethylaminobenzoyl,3-methoxy-4-ethoxybenzoyl, 3,4,5-trimethoxybenzoyl,p-dibutylaminobenzoyl, 3,4-diethoxyphenylacetyl,β-(3,4,5-trimethoxyphenyl)propionyl, o-iodobenzoyl, m-bromobenzoyl,p-chlorobenzoyl, p-fluorobenzoyl, 2-bromo-4-chlorobenzoyl,2,4,6-trichlorobenzoyl, p-chlorophenylacetyl,α-(m-bromophenyl)propionyl, p-trifluoromethylbenzoyl,2,4-di(trifluoromethyl)benzoyl, m-trifluoromethylphenylacetyl,β-(3-methyl-4-chlorophenyl)propionyl, p-dimethylaminobenzoyl,p-(N-methyl-N-ethylamino)benzoyl, o-acetamidobenzoyl,m-propionamidobenzoyl, 3-chloro-4-acetamidophenylacetyl,p-n-butoxybenzoyl, 2,4,6-triethoxybenzoyl,β-(p-trifluoromethylphenyl)propionyl, 2-methyl-4-methoxybenzoyl,p-acetamidophenylpropionyl and 3-chloro-4-ethoxybenzoyl.

When the hydroxyl protective group is a carbonate grouping, it has thestructural formula

i.e., it is an organic radical which can be considered to be derivedfrom a carbonic acid by removal of the hydroxyl group from the COOHportion. Y′ preferably represents alkyl having 1 to 7 carbon atoms;alkenyl having one or two double bonds and 2 to 7 carbon atoms;cycloalkyl-C_(r)H_(2r)—

wherein the cycloalkyl portion contains 3 to 7 ring atoms and r is zero,one, two or three; phenoxy; 2-, 3-, or 4-pyridyl; orphenyl-C_(r)H_(2r)—

wherein r is zero, one, two or three and phenyl is unsubstituted or issubstituted by 1 to 3 alkyl each having 1 to 4 carbon atoms, alkoxyhaving 1 to 4 carbon atoms, halo, trifluoromethyl, dialkylamino having 2to 8 carbon atoms or alkanoylamino having 2 to 6 carbon atoms. Mostpreferably, Y′ is C₁-C₇ alkyl, particularly ethyl or isopropyl.

Preferred protecting groups are those that can be selectively appendedto a functionality. These groups render such functionality inert tochemical reaction conditions to which the compound may be exposed. Afterthe protecting group has served its purpose it can be selectivelyremoved from the functionality without altering the molecular structure.Most preferred protecting groups are those that can be selectivelyappended to and removed from the functionality under mild conditions, inhigh yield.

Preferred protecting groups for 3-O-protected-naltrexone include thosethat are more stable and sterically hindered compared to an acetylprotecting group, which was found to be unstable during preparation andpurification, thus resulting in lower yield and purity, and difficultyin handling. Examples of preferred protecting groups for use in themethod of the present invention include isobutyryl, 2-methyl butyryl,tertbutyl carbonyl and the like. In a preferred embodiment, theprotecting group is isobutyryl, due to its greater stability whichresults in higher yield and purity. Such protecting groups provideyields of 3-O-protected-naltrexone of greater than 70, preferablygreater than 75%. In one embodiment, yield of 3-O-protected-naltrexoneis about 80% or greater.

Although some of the foregoing protecting groups and tertiary amines arenot substituted, those of ordinary skill in the art will understand thatsubstitutions can be present in some circumstances.

The present invention provides a method for stereoselective synthesis ofR-MNTX comprising;

(a) methylating a 3-O-protected-naltrexone with a methylating agent toyield 3-O-protected-R-MNTX salt; and

(b) hydrolysis to remove the 3-hydroxyl protecting group to yieldR-MNTX. Preferred hydroxyl protecting groups of the 3-O-protected-R-MNTXsalt include isobutyryl, 2-methyl butyryl, tertbutyl carbonyl, silylethers, 2-tetrahydropyranyl ethers, and alkyl carbonates.

Unlike the method described by Goldberg et al which teaches roomtemperature for three weeks or 70° C. for seven days for the methylationreaction to produce N-MNTX, the stereoselective methylation conditionsof the present invention are conducted at a temperature above 70° C.,more preferably above 80° C. In one embodiment, the reaction is carriedout at about 88° C. Based on the standard principles of chemicalreactions involving stereoisomers, one would expect at highertemperatures the reaction would proceed with kinetic control resultingin a mixture of R-MNTX and S-MNTX with high percentages of bothstereoisomers. It was surprising that at elevated temperatures themethod of the present invention provided predominantly the R-MNTX ratherthan a mixture with a higher percentage of S-MNTX.

The methylation reaction of the present invention is allowed to proceedfrom 1 hour to about 24 hours, preferably about 5 hours to about 16hours, more preferably about 8 to 12 hours, most preferably about 10hours. This reaction time offers a major industrial scale advantage overthe three weeks at room temperature or seven days at 70° C. taught byGoldberg et al.

In a preferred embodiment, the methylation reaction is conducted atabout 88° C. for 10 hours. These reaction parameters are highlydesirable for the development of a process amenable to scale-up inindustrial scale.

The present invention further provides a method of purifying R-MNTX froma mixture of stereoisomers of R-MNTX and S-MNTX, the method comprisingat least one, two or multiple recrystallizations. The recrystallizedproduct is highly enriched in R-MNTX and substantially devoid of S-MNTX.In one embodiment the recrystallized product is greater than 98% pureR-MNTX. It is understood that an artisan skilled in the art can optimizethis methodology to obtain higher purity and/or higher yield of R-MNTXin which the recrystallized product is greater than 99% pure R-MNTX andeven greater than 99.9% pure R-MNTX.

The recrystallization solvent can be an organic solvent or a mixture oforganic solvents or a mixture of organic solvent(s) plus water. Apreferred solvent is an alcohol, more preferred a low molecular weightalcohol. In one embodiment, the low molecular weight alcohol ismethanol.

Goldberg et al., and Cantrell et al., make use of organicsolvent(s)/water for recrystallization. This is a standard practice toclean up a reaction mixture. It is not the Goldberg et al's nor Cantrellet al's stated goal to obtain one stereoisomer over the other, as theydo not address the existence of stereoisomers, or whether a stereoisomeris obtained preferentially. Therefore, neither Goldberg et al., norCantrell et al., address the impact that recrystallization may have onthe composition of stereoisomers. The present invention discloses theconditions under which recrystallization can be used advantageously toincrease the purity of R-MNTX from a mixture of R-MNTX and S-MNTX.

One aspect of the invention is a method of resolving and identifyingR-MNTX and S-MNTX in a solution of MNTX. The R-MNTX also is useful inHPLC assay methods of quantifying an amount of R-MNTX in a compositionor mixture in which the method comprises applying a sample of thecomposition or mixture to a chromatography column, resolving thecomponents of the composition or mixture, and calculating the amount ofR-MNTX in the sample by comparing the percentage of a resolved componentin the sample with the percentage of a standard concentration of R-MNTX.The method is particularly useful in reverse phase HPLC chromatography.

The pharmaceutical preparations of the invention, when used alone or incocktails, are administered in therapeutically effective amounts. Atherapeutically effective amount will be determined by the parametersdiscussed below; but, in any event, is that amount which establishes alevel of the drug(s) effective for treating a subject, such as a humansubject, having one of the conditions described herein. An effectiveamount means that amount alone or with multiple doses, necessary todelay the onset of, lessen the severity of, or inhibit completely,lessen the progression of, or halt altogether the onset or progressionof the condition being treated or a symptom associated therewith. In thecase of constipation, an effective amount, for example, is that amountwhich relieves a symptom of constipation, which induces a bowelmovement, which increases the frequency of bowel movements, or whichdecreases oral-cecal transit time. The known and conventional definitionof constipation is (i) less than one bowel movement in the previousthree days or (ii) less than three bowel movements in the previous week(See e.g., U.S. Pat. No. 6,559,158). In other words, a patient is notconstipated (i.e., has “regular bowel movements” as used herein) if thepatient has at least one bowel movement every three days and at leastthree bowel movements per week. Accordingly, at least one bowel movementevery two days would be considered regular bowel movements. Likewise, atleast one bowel movement per day is a regular bowel movement. Effectiveamounts therefore can be those amounts necessary to establish ormaintain regular bowel movements.

In certain instances, the amount is sufficient to induce a bowelmovement within 12 hours of administration of the R-MNTX or the R-MNTXintermediate, 3-O-protected-R-MNTX salt, 10 hours, 8 hours, 6 hours, 4hours, 2 hours, 1 hour and even immediately upon administration,depending upon the mode of administration. Intravenous administrationcan produce an immediate effect of Taxation in chronic opioid users.Subcutaneous administration can result in a bowel movement within 12hours of administration, preferably within 4 hours of administration.When administered to a subject, effective amounts will depend, ofcourse, on the particular condition being treated; the severity of thecondition; individual patient parameters including age, physicalcondition, size and weight; concurrent treatment and, especially,concurrent treatment with opioids where opioids are administeredchronically; frequency of treatment; and the mode of administration.These factors are well known to those of ordinary skill in the art andcan be addressed with no more than routine experimentation.

Patients amenable to the therapy of the present invention include butare not limited to terminally ill patients, patients with advancedmedical illness, cancer patients, AIDS patients, post-operativepatients, patients with chronic pain, patients with neuropathies,patients with rheumatoid arthritis, patients with osteoarthritis,patients with chronic back pain, patients with spinal cord injury,patients with chronic abdominal pain, patients with chronic pancreaticpain, patients with pelvic/perineal pain, patients with fibromyalgia,patients with chronic fatigue syndrome, patients infected with HCV,patients with irritable bowel syndrome, patients with migraine ortension headaches, patients with sickle cell anemia, patients onhemodialysis, and the like.

Patients amenable to the therapy of the present invention also includebut are not limited to patients suffering from dysfunctions caused byendogenous opioids, especially in post-operative settings. In certainembodiments, the R-MNTX or intermediate thereof is present in an amountsufficient to accelerate discharge from hospital post-surgery, includingabdominal surgeries such as rectal resection, colectomy, stomach,esophageal, duodenal, appendectomy, hysterectomy, or non-abdominalsurgeries such as orthopedic, trauma injuries, thoracic ortransplantation surgery. This treatment can be effective to shorten thelength of the time in the hospital, or to shorten the time to a hospitaldischarge order written post-operatively by shortening the time to bowelsounds after surgery, or first flatus, to first laxation or to soliddiet intake following surgery. The R-MNTX or intermediate thereof maycontinue to be provided after the patient has ceased to receive opioidpain medications post-operatively.

Certain patients particularly amenable to treatment are patients havingthe symptoms of constipation and/or gastrointestinal immotility and whohave failed to obtain relief or ceased to obtain relief or a consistentdegree of relief of their symptoms using a laxative or a stool softener,either alone or in combination, or who are otherwise resistant tolaxatives and/or stool softeners. Such patients are said to berefractory to the conventional laxatives and/or stool softeners. Theconstipation and/or gastrointestinal immotility may be induced or aconsequence of one or more diverse conditions including, but not limitedto, a disease condition, a physical condition, a drug-induced condition,a physiological imbalance, stress, anxiety, and the like. The conditionsinducing constipation and/or gastrointestinal immotility may be acuteconditions or chronic conditions.

The subjects can be treated with a combination of R-MNTX, or the3-O-protected-R-MNTX intermediate thereof, and a laxative and/or a stoolsoftener (and optionally, an opioid). In these circumstances the R-MNTXor the intermediate thereof and the other therapeutic agent(s) areadministered close enough in time such that the subject experiences theeffects of the various agents as desired, which typically is at the sametime. In some embodiments the R-MNTX or the intermediate thereof will bedelivered first in time, in some embodiments second in time, and stillin some embodiments at the same time. As discussed in greater detailherein, the invention contemplates pharmaceutical preparations where theR-MNTX or intermediate thereof is administered in a formulationincluding the R-MNTX or the intermediate thereof and one or both of alaxative and a stool softener (and, optionally, an opioid). Theseformulations may be parenteral or oral, such as the ones described inU.S. Ser. No. 10/821,809. Included are solid, semisolid, liquid,controlled release, lyophilized and other such formulations.

In an important embodiment, the administered amount of R-MNTX issufficient to induce Taxation. This has particular application where thesubject is a chronic opioid user. Chronic opioid use as used hereinincludes daily opioid treatment for a week or more or intermittentopioid use for at least two weeks. It previously was determined thatpatients receiving opioids chronically become tolerant to opioids andneed increasing doses. Thus, a patient receiving oral doses of opioidschronically would be receiving typically between 40 and 100 mg per dayof a morphine-equivalent dose of opioid. It likewise was determinedsurprisingly that such subjects become more responsive to the effects ofMNTX and that surprisingly lower doses induced side effects. Thus, toinduce immediate Taxation, it requires on the order of only about 0.15mg/kg MNTX intravenously. For oral administration, a sufficient dose isbelieved to be less than 3 mg/kg uncoated and even less when the R-MNTXis enterically coated.

Patients using opioids chronically include late stage cancer patients,elderly patients with osteoarthritic changes, methadone maintenancepatients, neuropathic pain and chronic back pain patients. Treatment ofthese patients is important from a quality of life standpoint, as wellas to reduce complications arising from chronic constipation, such ashemorrhoids, appetite suppression, mucosal breakdown, sepsis, coloncancer risk, and myocardial infarction.

The opioid can be any pharmaceutically acceptable opioid. Common opioidsare those selected from the group consisting of alfentanil, anileridine,asimadoline, bremazocine, burprenorphine, butorphanol, codeine,dezocine, diacetylmorphine (heroin), dihydrocodeine, diphenoxylate,fedotozine, fentanyl, funaltrexamine, hydrocodone, hydromorphone,levallorphan, levomethadyl acetate, levorphanol, loperamide, meperidine(pethidine), methadone, morphine, morphine-6-glucoronide, nalbuphine,nalorphine, opium, oxycodone, oxymorphone, pentazocine, propiram,propoxyphene, remifentanyl, sufentanil, tilidine, trimebutine, andtramadol. The opioid also may be mixed together with the R-MNTX orintermediate thereof and provided in any of the forms described above inconnection with R-MNTX or intermediate thereof.

Generally, oral doses of R-MNTX and intermediates thereof will be fromabout 0.25 to about 19.0 mg/kg body weight per day. Generally,parenteral administration, including intravenous and subcutaneousadministration, will be from about 0.01 to 1.0 mg/kg body weightdepending on whether administration is as a bolus or is spread out overtime such as with an I.V. drip. Generally, the I.V. dose forpost-operative bowel dysfunction (POBD) is 0.3 mg/kg. It is expectedthat doses ranging from 0.01 to 0.45 mg/kg body weight will yield thedesired results. Dosage may be adjusted appropriately to achieve desireddrug levels, local or systemic, depending on the mode of administration.For example, it is expected that the dosage for oral administration ofthe opioid antagonists in an enterically-coated formulation would belower than in an immediate release oral formulation. In the event thatthe response in a patient is insufficient at such doses, even higherdoses (or effectively higher dosage by a different, more localizeddelivery route) may be employed to the extent that the patient tolerancepermits. Multiple doses per day are contemplated to achieve appropriatesystemic levels of compounds. Appropriate systemic levels can bedetermined by, for example, measurement of the patient's peak orsustained plasma level of the drug. Peak plasma levels below 100 ng/mlare preferred in some instances. “Dose” and “dosage” are usedinterchangeably herein.

A variety of administration routes are available. The particular modeselected will depend, of course, upon the particular combination ofdrugs selected, the severity of the condition being treated, orprevented, the condition of the patient, and the dosage required fortherapeutic efficacy. The methods of this invention, generally speaking,may be practiced using any mode of administration that is medicallyacceptable, meaning any mode that produces effective levels of theactive compounds without causing clinically unacceptable adverseeffects. Such modes of administration include oral, rectal, topical,transdermal, sublingual, intravenous infusion, pulmonary,intra-arterial, intra-adipose tissue, intra-lymphatic, intramuscular,intracavity, aerosol, aural (e.g., via eardrops), intranasal,inhalation, intra-articular, needleless injection, subcutaneous orintradermal (e.g., transdermal) delivery. For continuous infusion, apatient-controlled analgesia (PCA) device or an implantable drugdelivery device may be employed. Oral, rectal, or topical administrationmay be important for prophylactic or long-term treatment. Preferredrectal modes of delivery include administration as a suppository orenema wash.

The pharmaceutical preparations may conveniently be presented in unitdosage form and may be prepared by any of the methods well known in theart of pharmacy. All methods include the step of bringing the compoundsof the invention into association with a carrier which constitutes oneor more accessory ingredients. In general, the compositions are preparedby uniformly and intimately bringing the compounds of the invention intoassociation with a liquid carrier, a finely divided solid carrier, orboth, and then, if necessary, shaping the product.

When administered, the pharmaceutical preparations of the invention areapplied in pharmaceutically acceptable compositions. Such preparationsmay routinely contain salts, buffering agents, preservatives, compatiblecarriers, lubricants, and optionally other therapeutic ingredients. Whenused in medicine the salts should be pharmaceutically acceptable, butnon-pharmaceutically acceptable salts may conveniently be used toprepare pharmaceutically acceptable salts thereof and are not excludedfrom the scope of the invention. Such pharmacologically andpharmaceutically acceptable salts include, but are not limited to, thoseprepared from the following acids: hydrochloric, hydrobromic, sulfuric,nitric, phosphoric, maleic, acetic, salicylic, p-toluenesulfonic,tartaric, citric, methanesulfonic, formic, succinic,naphthalene-2-sulfonic, pamoic, 3-hydroxy-2-naphthalenecarboxylic, andbenzene sulfonic.

It should be understood that when referring to MNTX, R- and S-MNTX, andtherapeutic agent(s) of the invention, it is meant to encompass salts ofthe same. Such salts are of a variety well known to those or ordinaryskill in the art. When used in pharmaceutical preparations, the saltspreferably are pharmaceutically-acceptable for use in humans. Bromide isan example of one such salt.

The pharmaceutical preparations of the present invention may include orbe diluted into a pharmaceutically-acceptable carrier. The term“pharmaceutically-acceptable carrier” as used herein means one or morecompatible solid or liquid fillers, diluents or encapsulating substanceswhich are suitable for administration to a human or other mammal such asnon-human primate, a dog, cat, horse, cow, sheep, pig, or goat. The term“carrier” denotes an organic or inorganic ingredient, natural orsynthetic, with which the active ingredient is combined to facilitatethe application. The carriers are capable of being commingled with thepreparations of the present invention, and with each other, in a mannersuch that there is no interaction which would substantially impair thedesired pharmaceutical efficacy or stability. Carrier formulationssuitable for oral administration, for suppositories, and for parenteraladministration, etc., can be found in Remington's PharmaceuticalSciences, Mack Publishing Company, Easton, Pa.

Aqueous formulations may include a chelating agent, a buffering agent,an anti-oxidant and, optionally, an isotonicity agent, preferably pHadjusted to between 3.0 and 3.5. Examples of such formulations that arestable to autoclaving and long term storage are described in co-pendingU.S. application Ser. No. 10/821,811, entitled “PharmaceuticalFormulation.”

Chelating agents include, for example, ethylenediaminetetraacetic acid(EDTA) and derivatives thereof, citric acid and derivatives thereof,niacinamide and derivatives thereof, sodium desoxycholate andderivatives thereof, and L-glutamic acid, N,N-diacetic acid andderivatives thereof.

Buffering agents include those selected from the group consisting ofcitric acid, sodium citrate, sodium acetate, acetic acid, sodiumphosphate and phosphoric acid, sodium ascorbate, tartaric acid, maleicacid, glycine, sodium lactate, lactic acid, ascorbic acid, imidazole,sodium bicarbonate and carbonic acid, sodium succinate and succinicacid, histidine, and sodium benzoate and benzoic acid, or combinationsthereof.

Antioxidants include those selected from the group consisting of anascorbic acid derivative, butylated hydroxy anisole, butylated hydroxytoluene, alkyl gallate, sodium meta-bisulfite, sodium bisulfite, sodiumdithionite, sodium thioglycollate acid, sodium formaldehyde sulfoxylate,tocopheral and derivatives thereof, monothioglycerol, and sodiumsulfite. The preferred antioxidant is monothioglycerol.

Isotonicity agents include those selected from the group consisting ofsodium chloride, mannitol, lactose, dextrose, glycerol, and sorbitol.

Preservatives that can be used with the present compositions includebenzyl alcohol, parabens, thimerosal, chlorobutanol and preferablybenzalkonium chloride. Typically, the preservative will be present in acomposition in a concentration of up to about 2% by weight. The exactconcentration of the preservative, however, will vary depending upon theintended use and can be easily ascertained by one skilled in the art.

The compounds of the invention can be prepared in lyophilizedcompositions, preferably in the presence of a cryoprotecting agent suchas mannitol, or lactose, sucrose, polyethylene glycol, and polyvinylpyrrolidines. Cryoprotecting agents which result in a reconstitution pHof 6.0 or less are preferred. The invention therefore provides alyophilized preparation of therapeutic agent(s) of the invention. Thepreparation can contain a cryoprotecting agent, such as mannitol orlactose, which is preferably neutral or acidic in water.

Oral, parenteral and suppository formulations of agents are well knownand commercially available. The therapeutic agent(s) of the inventioncan be added to such well known formulations. It can be mixed togetherin solution or semi-solid solution in such formulations, can be providedin a suspension within such formulations or could be contained inparticles within such formulations.

A product containing therapeutic agent(s) of the invention and,optionally, one or more other active agents can be configured as an oraldosage. The oral dosage may be a liquid, a semisolid or a solid. Anopioid may optionally be included in the oral dosage. The oral dosagemay be configured to release the therapeutic agent(s) of the inventionbefore, after or simultaneously with the other agent (and/or theopioid). The oral dosage may be configured to have the therapeuticagent(s) of the invention and the other agents release completely in thestomach, release partially in the stomach and partially in theintestine, in the intestine, in the colon, partially in the stomach, orwholly in the colon. The oral dosage also may be configured whereby therelease of the therapeutic agent(s) of the invention is confined to thestomach or intestine while the release of the other active agent is notso confined or is confined differently from the therapeutic agent(s) ofthe invention. For example, the therapeutic agent(s) of the inventionmay be an enterically coated core or pellets contained within a pill orcapsule that releases the other agent first and releases the therapeuticagent(s) of the invention only after the therapeutic agent(s) of theinvention passes through the stomach and into the intestine. Thetherapeutic agent(s) of the invention also can be in a sustained releasematerial, whereby the therapeutic agent(s) of the invention is releasedthroughout the gastrointestinal tract and the other agent is released onthe same or a different schedule. The same objective for therapeuticagent(s) of the invention release can be achieved with immediate releaseof therapeutic agent(s) of the invention combined with enteric coatedtherapeutic agent(s) of the invention. In these instances, the otheragent could be released immediately in the stomach, throughout thegastrointestinal tract or only in the intestine.

The materials useful for achieving these different release profiles arewell known to those of ordinary skill in the art. Immediate release isobtainable by conventional tablets with binders which dissolve in thestomach. Coatings which dissolve at the pH of the stomach or whichdissolve at elevated temperatures will achieve the same purpose. Releaseonly in the intestine is achieved using conventional enteric coatingssuch as pH sensitive coatings which dissolve in the pH environment ofthe intestine (but not the stomach) or coatings which dissolve overtime. Release throughout the gastrointestinal tract is achieved by usingsustained-release materials and/or combinations of the immediate releasesystems and sustained and/or delayed intentional release systems (e.g.,pellets which dissolve at different pHs).

In the event that it is desirable to release the therapeutic agent(s) ofthe invention first, the therapeutic agent(s) of the invention could becoated on the surface of the controlled release formulation in anypharmaceutically acceptable carrier suitable for such coatings and forpermitting the release of the therapeutic agent(s) of the invention,such as in a temperature sensitive pharmaceutically acceptable carrierused for controlled release routinely. Other coatings which dissolvewhen placed in the body are well known to those of ordinary skill in theart.

The therapeutic agent(s) of the invention also may be mixed throughout acontrolled release formulation, whereby it is released before, after orsimultaneously with another agent. The therapeutic agent(s) of theinvention may be free, that is, solubilized within the material of theformulation. The therapeutic agent(s) of the invention also may be inthe form of vesicles, such as wax coated micropellets dispersedthroughout the material of the formulation. The coated pellets can befashioned to immediately release the therapeutic agent(s) of theinvention based on temperature, pH or the like. The pellets also can beconfigured so as to delay the release of the therapeutic agent(s) of theinvention, allowing the other agent a period of time to act before thetherapeutic agent(s) of the invention exerts its effects. Thetherapeutic agent(s) of the invention pellets also can be configured torelease the therapeutic agent(s) of the invention in virtually anysustained release pattern, including patterns exhibiting first orderrelease kinetics or sigmoidal order release kinetics using materials ofthe prior art and well known to those of ordinary skill in the art.

The therapeutic agent(s) of the invention also can be contained within acore within the controlled release formulation. The core may have anyone or any combination of the properties described above in connectionwith the pellets. The therapeutic agent(s) of the invention may be, forexample, in a core coated with a material, dispersed throughout amaterial, coated onto a material or adsorbed into or throughout amaterial.

It should be understood that the pellets or core may be of virtually anytype. They may be drug coated with a release material, drug interspersedthroughout material, drug adsorbed into a material, and so on. Thematerial may be erodible or nonerodible.

The therapeutic agent(s) of the invention, may be provided in particles.Particles as used herein means nano or microparticles (or in someinstances larger) which can consist in whole or in part of thetherapeutic agent(s) of the inventions or the other agents as describedherein. The particles may contain the therapeutic agent(s) in a coresurrounded by a coating, including, but not limited to, an entericcoating. The therapeutic agent(s) also may be dispersed throughout theparticles. The therapeutic agent(s) also may be adsorbed into theparticles. The particles may be of any order release kinetics, includingzero order release, first order release, second order release, delayedrelease, sustained release, immediate release, and any combinationthereof, etc. The particle may include, in addition to the therapeuticagent(s), any of those materials routinely used in the art of pharmacyand medicine, including, but not limited to, erodible, nonerodible,biodegradable, or nonbiodegradable material or combinations thereof. Theparticles may be microcapsules which contain the antagonist in asolution or in a semi-solid state. The particles may be of virtually anyshape.

Both non-biodegradable and biodegradable polymeric materials can be usedin the manufacture of particles for delivering the therapeutic agent(s).Such polymers may be natural or synthetic polymers. The polymer isselected based on the period of time over which release is desired.Bioadhesive polymers of particular interest include bioerodiblehydrogels described by H. S. Sawhney, C. P. Pathak and J. A. Hubell inMacromolecules, (1993) 26:581-587, the teachings of which areincorporated herein. These include polyhyaluronic acids, casein,gelatin, glutin, polyanhydrides, polyacrylic acid, alginate, chitosan,poly(methyl methacrylates), poly(ethyl methacrylates),poly(butylmethacrylate), poly(isobutyl methacrylate),poly(hexylmethacrylate), poly(isodecyl methacrylate), poly(laurylmethacrylate), poly(phenyl methacrylate), poly(methyl acrylate),poly(isopropyl acrylate), poly(isobutyl acrylate), and poly(octadecylacrylate).

The therapeutic agent(s) may be contained in controlled release systems.The term “controlled release” is intended to refer to anydrug-containing formulation in which the manner and profile of drugrelease from the formulation are controlled. This refers to immediate aswell as nonimmediate release formulations, with nonimmediate releaseformulations including but not limited to sustained release and delayedrelease formulations. The term “sustained release” (also referred to as“extended release”) is used in its conventional sense to refer to a drugformulation that provides for gradual release of a drug over an extendedperiod of time, and that preferably, although not necessarily, resultsin substantially constant blood levels of a drug over an extended timeperiod. The term “delayed release” is used in its conventional sense torefer to a drug formulation in which there is a time delay betweenadministration of the formulation and the release of the drug therefrom.“Delayed release” may or may not involve gradual release of drug over anextended period of time, and thus may or may not be “sustained release.”These formulations may be for any mode of administration.

Delivery systems specific for the gastrointestinal tract are roughlydivided into three types: the first is a delayed release system designedto release a drug in response to, for example, a change in pH; thesecond is a timed-release system designed to release a drug after apredetermined time; and the third is a microflora enzyme system makinguse of the abundant enterobacteria in the lower part of thegastrointestinal tract (e.g., in a colonic site-directed releaseformulation).

An example of a delayed release system is one that uses, for example, anacrylic or cellulosic coating material and dissolves on pH change.Because of ease of preparation, many reports on such “enteric coatings”have been made. In general, an enteric coating is one which passesthrough the stomach without releasing substantial amounts of drug in thestomach (i.e., less than 10% release, 5% release and even 1% release inthe stomach) and sufficiently disintegrating in the intestinal tract (bycontact with approximately neutral or alkaline intestine juices) toallow the transport (active or passive) of the active agent through thewalls of the intestinal tract.

Various in vitro tests for determining whether or not a coating isclassified as an enteric coating have been published in thepharmacopoeia of various countries. A coating which remains intact forat least 2 hours, in contact with artificial gastric juices such as HClof pH 1 at 36 to 38° C. and thereafter disintegrates within 30 minutesin artificial intestinal juices such as a KH₂PO₄ buffered solution of pH6.8 is one example. One such well known system is EUDRAGIT material,commercially available and reported on by Behringer, ManchesterUniversity, Saale Co., and the like. Enteric coatings are discussedfurther, below.

A timed release system is represented by Time Erosion System (TES) byFujisawa Pharmaceutical Co., Ltd. and Pulsincap by R. P. Scherer.According to these systems, the site of drug release is decided by thetime of transit of a preparation in the gastrointestinal tract. Sincethe transit of a preparation in the gastrointestinal tract is largelyinfluenced by the gastric emptying time, some time release systems arealso enterically coated.

Systems making use of the enterobacteria can be classified into thoseutilizing degradation of azoaromatic polymers by an azo reductaseproduced from enterobacteria as reported by the group of Ohio University(M. Saffran, et al., Science, Vol. 233: 1081 (1986)) and the group ofUtah University (J. Kopecek, et al., Pharmaceutical Research, 9(12),1540-1545 (1992)); and those utilizing degradation of polysaccharides bybeta-galactosidase of enterobacteria as reported by the group of HebrewUniversity (unexamined published Japanese patent application No. 5-50863based on a PCT application) and the group of Freiberg University (K. H.Bauer et al., Pharmaceutical Research, 10(10), S218 (1993)). Inaddition, the system using chitosan degradable by chitosanase by TeikokuSeiyaku K. K. (unexamined published Japanese patent application No.4-217924 and unexamined published Japanese patent application No.4-225922) is also included.

The enteric coating is typically, although not necessarily, a polymericmaterial. Preferred enteric coating materials comprise bioerodible,gradually hydrolyzable and/or gradually water-soluble polymers. The“coating weight,” or relative amount of coating material per capsule,generally dictates the time interval between ingestion and drug release.Any coating should be applied to a sufficient thickness such that theentire coating does not dissolve in the gastrointestinal fluids at pHbelow about 5, but does dissolve at pH about 5 and above. It is expectedthat any anionic polymer exhibiting a pH-dependent solubility profilecan be used as an enteric coating in the practice of the presentinvention. The selection of the specific enteric coating material willdepend on the following properties: resistance to dissolution anddisintegration in the stomach; impermeability to gastric fluids anddrug/carrier/enzyme while in the stomach; ability to dissolve ordisintegrate rapidly at the target intestine site; physical and chemicalstability during storage; non-toxicity; ease of application as a coating(substrate friendly); and economical practicality.

Suitable enteric coating materials include, but are not limited to:cellulosic polymers such as cellulose acetate phthalate, celluloseacetate trimellitate, hydroxypropylmethyl cellulose phthalate,hydroxypropyhmethyl cellulose succinate and carboxymethylcellulosesodium; acrylic acid polymers and copolymers, preferably formed fromacrylic acid, methacrylic acid, methyl acrylate, ammoniummethylacrylate, ethyl acrylate, methyl methacrylate and/or ethylmethacrylate (e.g., those copolymers sold under the trade nameEUDRAGIT); vinyl polymers and copolymers such as polyvinyl acetate,polyvinylacetate phthalate, vinylacetate crotonic acid copolymer, andethylene-vinyl acetate copolymers; and shellac (purified lac).Combinations of different coating materials may also be used. Well knownenteric coating material for use herein are those acrylic acid polymersand copolymers available under the trade name EUDRAGIT from Rohm Pharma(Germany). The EUDRAGIT series E, L, S, RL, RS and NE copolymers areavailable as solubilized in organic solvent, as an aqueous dispersion,or as a dry powder. The EUDRAGIT series RL, NE, and RS copolymers areinsoluble in the gastrointestinal tract but are permeable and are usedprimarily for extended release. The EUDRAGIT series E copolymersdissolve in the stomach. The EUDRAGIT series L, L-30D and S copolymersare insoluble in stomach and dissolve in the intestine, and are thusmost preferred herein.

A particular methacrylic copolymer is EUDRAGIT L, particularly L-30D andEUDRAGIT L 100-55. In EUDRAGIT L-30D, the ratio of free carboxyl groupsto ester groups is approximately 1:1. Further, the copolymer is known tobe insoluble in gastrointestinal fluids having pH below 5.5, generally1.5-5.5, i.e., the pH generally present in the fluid of the uppergastrointestinal tract, but readily soluble or partially soluble at pHabove 5.5, i.e., the pH generally present in the fluid of lowergastrointestinal tract. Another particular methacrylic acid polymer isEUDRAGIT S, which differs from EUDRAGIT L-30D in that the ratio of freecarboxyl groups to ester groups is approximately 1:2. EUDRAGIT S isinsoluble at pH below 5.5, but unlike EUDRAGIT L-30D, is poorly solublein gastrointestinal fluids having a pH in the range of 5.5 to 7.0, suchas in the small intestine. This copolymer is soluble at pH 7.0 andabove, i.e., the pH generally found in the colon. EUDRAGIT S can be usedalone as a coating to provide drug delivery in the large intestine.Alternatively, EUDRAGIT S, being poorly soluble in intestinal fluidsbelow pH 7, can be used in combination with EUDRAGIT L-30D, soluble inintestinal fluids above pH 5.5, in order to provide a delayed releasecomposition which can be formulated to deliver the active agent tovarious segments of the intestinal tract. The more EUDRAGIT L-30D used,the more proximal release and delivery begins, and the more EUDRAGIT Sused, the more distal release and delivery begins. It will beappreciated by those skilled in the art that both EUDRAGIT L-30D andEUDRAGIT S can be replaced with other pharmaceutically acceptablepolymers having similar pH solubility characteristics. In certainembodiments of the invention, the preferred enteric coating isACRYL-EZE™ (methacrylic acid co-polymer type C; Colorcon, West Point,Pa.).

The enteric coating provides for controlled release of the active agent,such that drug release can be accomplished at some generally predictablelocation. The enteric coating also prevents exposure of the therapeuticagent and carrier to the epithelial and mucosal tissue of the buccalcavity, pharynx, esophagus, and stomach, and to the enzymes associatedwith these tissues. The enteric coating therefore helps to protect theactive agent, carrier and a patient's internal tissue from any adverseevent prior to drug release at the desired site of delivery.Furthermore, the coated material of the present invention allowsoptimization of drug absorption, active agent protection, and safety.Multiple enteric coatings targeted to release the active agent atvarious regions in the gastrointestinal tract would enable even moreeffective and sustained improved delivery throughout thegastrointestinal tract.

The coating can, and usually does, contain a plasticizer to prevent theformation of pores and cracks that would permit the penetration of thegastric fluids. Suitable plasticizers include, but are not limited to,triethyl citrate (Citroflex 2), triacetin (glyceryl triacetate), acetyltriethyl citrate (Citroflec A2), Carbowax 400 (polyethylene glycol 400),diethyl phthalate, tributyl citrate, acetylated monoglycerides,glycerol, fatty acid esters, propylene glycol, and dibutyl phthalate. Inparticular, a coating comprised of an anionic carboxylic acrylic polymerwill usually contain approximately 10% to 25% by weight of aplasticizer, particularly dibutyl phthalate, polyethylene glycol,triethyl citrate and triacetin. The coating can also contain othercoating excipients such as detackifiers, antifoaming agents, lubricants(e.g., magnesium stearate), and stabilizers (e.g.,hydroxypropylcellulose, acids and bases) to solubilize or disperse thecoating material, and to improve coating performance and the coatedproduct.

The coating can be applied to particles of the therapeutic agent(s),tablets of the therapeutic agent(s), capsules containing the therapeuticagent(s) and the like, using conventional coating methods and equipment.For example, an enteric coating can be applied to a capsule using acoating pan, an airless spray technique, fluidized bed coatingequipment, or the like. Detailed information concerning materials,equipment and processes for preparing coated dosage forms may be foundin Pharmaceutical Dosage Forms: Tablets, eds. Lieberman et al. (NewYork: Marcel Dekker, Inc., 1989), and in Ansel et al., PharmaceuticalDosage Forms and Drug Delivery Systems, 6th Ed. (Media, Pa.: Williams &Wilkins, 1995). The coating thickness, as noted above, must besufficient to ensure that the oral dosage form remains intact until thedesired site of topical delivery in the lower intestinal tract isreached.

In another embodiment, drug dosage forms are provided that comprise anenterically coated, osmotically activated device housing a formulationof the invention. In this embodiment, the drug-containing formulation isencapsulated in a semipermeable membrane or barrier containing a smallorifice. As known in the art with respect to so-called “osmotic pump”drug delivery devices, the semipermeable membrane allows passage ofwater in either direction, but not drug. Therefore, when the device isexposed to aqueous fluids, water will flow into the device due to theosmotic pressure differential between the interior and exterior of thedevice. As water flows into the device, the drug-containing formulationin the interior will be “pumped” out through the orifice. The rate ofdrug release will be equivalent to the inflow rate of water times thedrug concentration. The rate of water influx and drug efflux can becontrolled by the composition and size of the orifice of the device.Suitable materials for the semipermeable membrane include, but are notlimited to, polyvinyl alcohol, polyvinyl chloride, semipermeablepolyethylene glycols, semipermeable polyurethanes, semipermeablepolyamides, semipermeable sulfonated polystyrenes and polystyrenederivatives; semipermeable poly(sodium styrenesulfonate), semipermeablepoly(vinylbenzyltrimethylammonium chloride), and cellulosic polymerssuch as cellulose acetate, cellulose diacetate, cellulose triacetate,cellulose propionate, cellulose acetate propionate, cellulose acetatebutyrate, cellulose trivalerate, cellulose trilmate, cellulosetripalmitate, cellulose trioctanoate, cellulose tripropionate, cellulosedisuccinate, cellulose dipalmitate, cellulose dicylate, celluloseacetate succinate, cellulose propionate succinate, cellulose acetateoctanoate, cellulose valerate palmitate, cellulose acetate heptanate,cellulose acetaldehyde dimethyl acetal, cellulose acetateethylcarbamate, cellulose acetate methylcarbamate, cellulosedimethylaminoacetate and ethylcellulose.

In another embodiment, drug dosage forms are provided that comprise asustained release coated device housing a formulation of the invention.In this embodiment, the drug-containing formulation is encapsulated in asustained release membrane or film. The membrane may be semipermeable,as described above. A semipermeable membrane allows for the passage ofwater inside the coated device to dissolve the drug. The dissolved drugsolution diffuses out through the semipermeable membrane. The rate ofdrug release depends upon the thickness of the coated film and therelease of drug can begin in any part of the GI tract. Suitable membranematerials for such a membrane include ethylcellulose.

In another embodiment, drug dosage forms are provided that comprise asustained release device housing a formulation of the invention. In thisembodiment, the drug-containing formulation is uniformly mixed with asustained release polymer. These sustained release polymers are highmolecular weight water-soluble polymers, which when in contact withwater, swell and create channels for water to diffuse inside anddissolve the drug. As the polymers swell and dissolve in water, more ofdrug is exposed to water for dissolution. Such a system is generallyreferred to as sustained release matrix. Suitable materials for such adevice include hydropropyl methylcellulose, hydroxypropyl cellulose,hydroxyethyl cellulose and methyl cellulose.

In another embodiment, drug dosage forms are provided that comprise anenteric coated device housing a sustained release formulation of theinvention. In this embodiment, the drug containing product describedabove is coated with an enteric polymer. Such a device would not releaseany drug in the stomach and when the device reaches the intestine, theenteric polymer is first dissolved and only then would the drug releasebegin. The drug release would take place in a sustained release fashion.

Enterically coated, osmotically activated devices can be manufacturedusing conventional materials, methods and equipment. For example,osmotically activated devices may be made by first encapsulating, in apharmaceutically acceptable soft capsule, a liquid or semi-solidformulation of the compounds of the invention as described previously.This interior capsule is then coated with a semipermeable membranecomposition (comprising, for example, cellulose acetate and polyethyleneglycol 4000 in a suitable solvent such as a methylene chloride-methanoladmixture), for example using an air suspension machine, until asufficiently thick laminate is formed, e.g., around 0.05 mm. Thesemipermeable laminated capsule is then dried using conventionaltechniques. Then, an orifice having a desired diameter (e.g., about 0.99mm) is provided through the semipermeable laminated capsule wall, using,for example, mechanical drilling, laser drilling, mechanical rupturing,or erosion of an erodible element such as a gelatin plug. Theosmotically activated device may then be enterically coated aspreviously described. For osmotically activated devices containing asolid carrier rather than a liquid or semi-solid carrier, the interiorcapsule is optional; that is, the semipermeable membrane may be formeddirectly around the carrier-drug composition. However, preferredcarriers for use in the drug-containing formulation of the osmoticallyactivated device are solutions, suspensions, liquids, immiscibleliquids, emulsions, sols, colloids, and oils. Particularly preferredcarriers include, but are not limited to, those used for entericallycoated capsules containing liquid or semisolid drug formulations.

Cellulose coatings include those of cellulose acetate phthalate andtrimellitate; methacrylic acid copolymers, e.g. copolymers derived frommethylacrylic acid and esters thereof, containing at least 40%methylacrylic acid; and especially hydroxypropyl methylcellulosephthalate. Methylacrylates include those of molecular weight above100,000 daltons based on, e.g. methylacrylate and methyl or ethylmethylacrylate in a ratio of about 1:1. Typical products includeEndragit L, e.g. L 100-55, marketed by Rohm GmbH, Darmstadt, Germany.Typical cellulose acetate phthalates have an acetyl content of 17-26%and a phthalate content of from 30-40% with a viscosity of ca. 45-90 cP.Typical cellulose acetate trimellitates have an acetyl content of17-26%, a trimellityl content from 25-35% with a viscosity of ca. 15-20cS. An example of a cellulose acetate trimellitate is the marketedproduct CAT (Eastman Kodak Company, USA). Hydroxypropyl methylcellulosephthalates typically have a molecular weight of from 20,000 to 130,000daltons, a hydroxypropyl content of from 5 to 10%, a methoxy content offrom 18 to 24% and a phthalyl content from 21 to 35%. An example of acellulose acetate phthalate is the marketed product CAP (Eastman Kodak,Rochester N.Y., USA). Examples of hydroxypropyl methylcellulosephthalates are the marketed products having a hydroxypropyl content offrom 6-10%, a methoxy content of from 20-24%, a phthalyl content of from21-27%, a molecular weight of about 84,000 daltons, sold under thetrademark HP50 and available from Shin-Etsu Chemical Co. Ltd., Tokyo,Japan, and having a hydroxypropyl content, a methoxyl content, and aphthalyl content of 5-9%, 18-22% and 27-35%, respectively, and amolecular weight of 78,000 daltons, known under the trademark HP55 andavailable from the same supplier.

The therapeutic agents may be provided in capsules, coated or not. Thecapsule material may be either hard or soft, and as will be appreciatedby those skilled in the art, typically comprises a tasteless, easilyadministered and water soluble compound such as gelatin, starch or acellulosic material. The capsules are preferably sealed, such as withgelatin bands or the like. See, for example, Remington: The Science andPractice of Pharmacy, Nineteenth Edition (Easton, Pa.: Mack PublishingCo., 1995), which describes materials and methods for preparingencapsulated pharmaceuticals.

A product containing therapeutic agent(s) of the invention can beconfigured as a suppository. The therapeutic agent(s) of the inventioncan be placed anywhere within or on the suppository to favorably affectthe relative release of the therapeutic agent(s). The nature of therelease can be zero order, first order, or sigmoidal, as desired.

Suppositories are solid dosage forms of medicine intended foradministration via the rectum. Suppositories are compounded so as tomelt, soften, or dissolve in the body cavity (around 98.6° F.) therebyreleasing the medication contained therein. Suppository bases should bestable, nonirritating, chemically inert, and physiologically inert. Manycommercially available suppositories contain oily or fatty basematerials, such as cocoa butter, coconut oil, palm kernel oil, and palmoil, which often melt or deform at room temperature necessitating coolstorage or other storage limitations. U.S. Pat. No. 4,837,214 to Tanakaet al. describes a suppository base comprised of 80 to 99 percent byweight of a lauric-type fat having a hydroxyl value of 20 or smaller andcontaining glycerides of fatty acids having 8 to 18 carbon atomscombined with 1 to 20 percent by weight diglycerides of fatty acids(which erucic acid is an example of). The shelf life of these type ofsuppositories is limited due to degradation. Other suppository basescontain alcohols, surfactants, and the like which raise the meltingtemperature but also can lead to poor absorption of the medicine andside effects due to irritation of the local mucous membranes (see forexample, U.S. Pat. No. 6,099,853 to Hartelendy et al., U.S. Pat. No.4,999,342 to Ahmad et al., and U.S. Pat. No. 4,765,978 to Abidi et al.).

The base used in the pharmaceutical suppository composition of thisinvention includes, in general, oils and fats comprising triglyceridesas main components such as cacao butter, palm fat, palm kernel oil,coconut oil, fractionated coconut oil, lard and WITEPSOL®, waxes such aslanolin and reduced lanolin; hydrocarbons such as VASELINE®, squalene,squalane and liquid paraffin; long to medium chain fatty acids such ascaprylic acid, lauric acid, stearic acid and oleic acid; higher alcoholssuch as lauryl alcohol, cetanol and stearyl alcohol; fatty acid esterssuch as butyl stearate and dilauryl malonate; medium to long chaincarboxylic acid esters of glycerin such as triolein and tristearin;glycerin-substituted carboxylic acid esters such as glycerinacetoacetate; and polyethylene glycols and its derivatives such asmacrogols and cetomacrogol. They may be used either singly or incombination of two or more. If desired, the composition of thisinvention may further include a surface-active agent, a coloring agent,etc., which are ordinarily used in suppositories.

The pharmaceutical composition of this invention may be prepared byuniformly mixing predetermined amounts of the active ingredient, theabsorption aid and optionally the base, etc. in a stirrer or a grindingmill, if required at an elevated temperature. The resulting composition,may be formed into a suppository in unit dosage form by, for example,casting the mixture in a mold, or by forming it into a gelatin capsuleusing a capsule filling machine.

The compositions according to the present invention also can beadministered as a nasal spray, nasal drop, suspension, gel, ointment,cream or powder. The administration of a composition can also includeusing a nasal tampon or a nasal sponge containing a composition of thepresent invention.

The nasal delivery systems that can be used with the present inventioncan take various forms including aqueous preparations, non-aqueouspreparations and combinations thereof. Aqueous preparations include, forexample, aqueous gels, aqueous suspensions, aqueous liposomaldispersions, aqueous emulsions, aqueous microemulsions and combinationsthereof. Non-aqueous preparations include, for example, non-aqueousgels, non-aqueous suspensions, non-aqueous liposomal dispersions,non-aqueous emulsions, non-aqueous microemulsions and combinationsthereof. The various forms of the nasal delivery systems can include abuffer to maintain pH, a pharmaceutically acceptable thickening agentand a humectant. The pH of the buffer can be selected to optimize theabsorption of the therapeutic agent(s) across the nasal mucosa.

With respect to the non-aqueous nasal formulations, suitable forms ofbuffering agents can be selected such that when the formulation isdelivered into the nasal cavity of a mammal, selected pH ranges areachieved therein upon contact with, e.g., a nasal mucosa. In the presentinvention, the pH of the compositions should be maintained from about2.0 to about 6.0. It is desirable that the pH of the compositions is onewhich does not cause significant irritation to the nasal mucosa of arecipient upon administration.

The viscosity of the compositions of the present invention can bemaintained at a desired level using a pharmaceutically acceptablethickening agent. Thickening agents that can be used in accordance withthe present invention include methyl cellulose, xanthan gum,carboxymethyl cellulose, hydroxypropyl cellulose, carbomer, polyvinylalcohol, alginates, acacia, chitosans and combinations thereof. Theconcentration of the thickening agent will depend upon the agentselected and the viscosity desired. Such agents can also be used in apowder formulation discussed above.

The compositions of the present invention can also include a humectantto reduce or prevent drying of the mucus membrane and to preventirritation thereof. Suitable humectants that can be used in the presentinvention include sorbitol, mineral oil, vegetable oil and glycerol;soothing agents; membrane conditioners; sweeteners; and combinationsthereof. The concentration of the humectant in the present compositionswill vary depending upon the agent selected.

One or more therapeutic agents may be incorporated into the nasaldelivery system or any other delivery system described herein.

A composition formulated for topical administration may be liquid orsemi-solid (including, for example, a gel, lotion, emulsion, cream,ointment, spray or aerosol) or may be provided in combination with a“finite” carrier, for example, a non-spreading material that retains itsform, including, for example, a patch, bioadhesive, dressing or bandage.It may be aqueous or non-aqueous; it may be formulated as a solution,emulsion, dispersion, a suspension or any other mixture.

Important modes of administration include topical application to theskin, eyes or mucosa. Thus, typical vehicles are those suitable forpharmaceutical or cosmetic application to body surfaces. Thecompositions provided herein may be applied topically or locally tovarious areas in the body of a patient. As noted above, topicalapplication is intended to refer to application to the tissue of anaccessible body surface, such as, for example, the skin (the outerintegument or covering) and the mucosa (the mucous-producing, secretingand/or containing surfaces). Exemplary mucosal surfaces include themucosal surfaces of the eyes, mouth (such as the lips, tongue, gums,cheeks, sublingual and roof of the mouth), larynx, esophagus, bronchial,nasal passages, vagina and rectum/anus; in some embodiments, preferablythe mouth, larynx, esophagus, vagina and rectum/anus; in otherembodiments, preferably the eyes, larynx, esophagus, bronchial, nasalpassages, and vagina and rectum/anus. As noted above, local applicationherein refers to application to a discrete internal area of the body,such as, for example, a joint, soft tissue area (such as muscle, tendon,ligaments, intraocular or other fleshy internal areas), or otherinternal area of the body. Thus, as used herein, local applicationrefers to applications to discrete areas of the body.

With respect to topical and/or local administration of the presentcompositions, desirable efficacy may involve, for example, penetrationof therapeutic agent(s) of the invention into the skin and/or tissue tosubstantially reach a hyperalgesic site to provide desirableanti-hyperalgesic pain relief. The efficacy of the present compositionsmay be about the same as that achieved, for example, with central opiateanalgesics. But, as discussed in detail herein, the efficacy achievedwith therapeutic agent(s) of the invention is preferably obtainedwithout the undesirable effects that are typically associated withcentral opiates including, for example, respiratory depression,sedation, and addiction, as it is believed that therapeutic agent(s) ofthe invention does not cross the blood brain barrier.

Also in certain preferred embodiments, including embodiments thatinvolve aqueous vehicles, the compositions may also contain a glycol,that is, a compound containing two or more hydroxy groups. A glycolwhich is particularly preferred for use in the compositions is propyleneglycol. In these preferred embodiments, the glycol is preferablyincluded in the compositions in a concentration of from greater than 0to about 5 wt. %, based on the total weight of the composition. Morepreferably, the compositions contain from about 0.1 to less than about 5wt. % of a glycol, with from about 0.5 to about 2 wt. % being even morepreferred. Still more preferably, the compositions contain about 1 wt. %of a glycol.

For local internal administration, such as intra-articularadministration, the compositions are preferably formulated as a solutionor a suspension in an aqueous-based medium, such as isotonicallybuffered saline or are combined with a biocompatible support orbioadhesive intended for internal administration.

Lotions, which, for example, may be in the form of a suspension,dispersion or emulsion, contain an effective concentration of one ormore of the compounds. The effective concentration is preferably todeliver an effective amount, typically at a concentration of betweenabout 0.1-50% [by weight] or more of one or more of the compoundsprovided herein. The lotions also contain [by weight] from 1% to 50% ofan emollient and the balance water, a suitable buffer, and other agentsas described above. Any emollients known to those of skill in the art assuitable for application to human skin may be used. These include, butare not limited to, the following: (a) Hydrocarbon oils and waxes,including mineral oil, petrolatum, paraffin, ceresin, ozokerite,microcrystalline wax, polyethylene, and perhydrosqualene. b) Siliconeoils, including dimethylpolysiloxanes, methylphenylpolysiloxanes,water-soluble and alcohol-soluble silicone-glycol copolymers. (c)Triglyceride fats and oils, including those derived from vegetable,animal and marine sources. Examples include, but are not limited to,castor oil, safflower oil, cotton seed oil, corn oil, olive oil, codliver oil, almond oil, avocado oil, palm oil, sesame oil, and soybeanoil. (d) Acetoglyceride esters, such as acetylated monoglycerides. (e)Ethoxylated glycerides, such as ethoxylated glyceryl monstearate. (f)Alkyl esters of fatty acids having 10 to 20 carbon atoms. Methyl,isopropyl and butyl esters of fatty acids are useful herein. Examplesinclude, but are not limited to, hexyl laurate, isohexyl laurate,isohexyl palmitate, isopropyl palmitate, isopropyl myristate, decyloleate, isodecyl oleate, hexadecyl stearate, decyl stearate, isopropylisostearate, diisopropyl adipate, diisohexyl adipate, dihexyldecyladipate, diisopropyl sebacate, lauryl lactate, myristyl lactate, andcetyl lactate. (g) Alkenyl esters of fatty acids having 10 to 20 carbonatoms. Examples thereof include, but are not limited to, oleylmyristate, oleyl stearate, and oleyl oleate. (h) Fatty acids having 9 to22 carbon atoms. Suitable examples include, but are not limited to,pelargonic, lauric, myristic, palmitic, stearic, isostearic,hydroxystearic, oleic, linoleic, ricinoleic, arachidonic, behenic, anderucic acids. (i) Fatty alcohols having 10 to 22 carbon atoms, such as,but not limited to, lauryl, myristyl, cetyl, hexadecyl, stearyl,isostearyl, hydroxystearyl, oleyl, ricinoleyl, behenyl, erucyl, and2-octyl dodecyl alcohols. (j) Fatty alcohol ethers, including, but notlimited to ethoxylated fatty alcohols of 10 to 20 carbon atoms, such as,but are not limited to, the lauryl, cetyl, stearyl, isostearyl, oleyl,and cholesterol alcohols having attached thereto from 1 to 50 ethyleneoxide groups or 1 to 50 propylene oxide groups or mixtures thereof. (k)Ether-esters, such as fatty acid esters of ethoxylated fatty alcohols.(l) Lanolin and derivatives, including, but not limited to, lanolin,lanolin oil, lanolin wax, lanolin alcohols, lanolin fatty acids,isopropyl lanolate, ethoxylated lanolin, ethoxylated lanolin alcohols,ethoxylated cholesterol, propoxylated lanolin alcohols, acetylatedlanolin, acetylated lanolin alcohols, lanolin alcohols linoleate,lanolin alcohols ricinoleate, acetate of lanolin alcohols ricinoleate,acetate of ethoxylated alcohols-esters, hydrogenolysis of lanolin,ethoxylated hydrogenated lanolin, ethoxylated sorbitol lanolin, andliquid and semisolid lanolin absorption bases. (m) polyhydric alcoholsand polyether derivatives, including, but not limited to, propyleneglycol, dipropylene glycol, polypropylene glycol [M.W. 2000-4000],polyoxyethylene polyoxypropylene glycols, polyoxypropylenepolyoxyethylene glycols, glycerol, ethoxylated glycerol, propoxylatedglycerol, sorbitol, ethoxylated sorbitol, hydroxypropyl sorbitol,polyethylene glycol [M.W. 200-6000], methoxy polyethylene glycols 350,550, 750, 2000, 5000, poly(ethylene oxide) homopolymers [M.W.100,000-5,000,000], polyalkylene glycols and derivatives, hexyleneglycol (2-methyl-2,4-pentanediol), 1,3-butylene glycol,1,2,6,-hexanetriol, ethohexadiol USP (2-ethyl-1,3-hexanediol), C.sub.15-C.sub.18 vicinal glycol and polyoxypropylene derivatives oftrimethylolpropane. (n) polyhydric alcohol esters, including, but notlimited to, ethylene glycol mono- and di-fatty acid esters, diethyleneglycol mono- and di-fatty acid esters, polyethylene glycol [M.W.200-6000], mono- and di-fatty esters, propylene glycol mono- anddi-fatty acid esters, polypropylene glycol 2000 monooleate,polypropylene glycol 2000 monostearate, ethoxylated propylene glycolmonostearate, glyceryl mono- and di-fatty acid esters, polyglycerolpoly-fatty acid esters, ethoxylated glyceryl monostearate, 1,3-butyleneglycol monostearate, 1,3-butylene glycol distearate, polyoxyethylenepolyol fatty acid ester, sorbitan fatty acid esters, and polyoxyethylenesorbitan fatty acid esters. (o) Wax esters, including, but not limitedto, beeswax, spermaceti, myristyl myristate, and stearyl stearate andbeeswax derivatives, including, but not limited to, polyoxyethylenesorbitol beeswax, which are reaction products of beeswax withethoxylated sorbitol of varying ethylene oxide content that form amixture of ether-esters. (p) Vegetable waxes, including, but not limitedto, carnauba and candelilla waxes. (q) phospholipids, such as lecithinand derivatives. (r) Sterols, including, but not limited to, cholesteroland cholesterol fatty acid esters. (s) Amides, such as fatty acidamides, ethoxylated fatty acid amides, and solid fatty acidalkanolamides.

The lotions further preferably contain [by weight] from 1% to 10%, morepreferably from 2% to 5%, of an emulsifier. The emulsifiers can benonionic, anionic or cationic. Examples of satisfactory nonionicemulsifiers include, but are not limited to, fatty alcohols having 10 to20 carbon atoms, fatty alcohols having 10 to 20 carbon atoms condensedwith 2 to 20 moles of ethylene oxide or propylene oxide, alkyl phenolswith 6 to 12 carbon atoms in the alkyl chain condensed with 2 to 20moles of ethylene oxide, mono- and di-fatty acid esters of ethyleneoxide, mono- and di-fatty acid esters of ethylene glycol where the fattyacid moiety contains from 10 to 20 carbon atoms, diethylene glycol,polyethylene glycols of molecular weight 200 to 6000, propylene glycolsof molecular weight 200 to 3000, glycerol, sorbitol, sorbitan,polyoxyethylene sorbitol, polyoxyethylene sorbitan and hydrophilic waxesters. Suitable anionic emulsifiers include, but are not limited to,the fatty acid soaps, e.g., sodium, potassium and triethanolamine soaps,where the fatty acid moiety contains from 10 to 20 carbon atoms. Othersuitable anionic emulsifiers include, but are not limited to, the alkalimetal, ammonium or substituted ammonium alkyl sulfates, alkylarylsulfonates, and alkyl ethoxy ether sulfonates having 10 to 30 carbonatoms in the alkyl moiety. The alkyl ethoxy ether sulfonates containfrom 1 to 50 ethylene oxide units. Among satisfactory cationicemulsifiers are quaternary ammonium, morpholinium and pyridiniumcompounds. Certain of the emollients described in preceding paragraphsalso have emulsifying properties. When a lotion is formulated containingsuch an emollient, an additional emulsifier is not needed, though it canbe included in the composition.

The balance of the lotion is water or a C₂ or C₃ alcohol, or a mixtureof water and the alcohol. The lotions are formulated by simply admixingall of the components together. Preferably the compound, such asloperamide, is dissolved, suspended or otherwise uniformly dispersed inthe mixture.

Other conventional components of such lotions may be included. One suchadditive is a thickening agent at a level from 1% to 10% by weight ofthe composition. Examples of suitable thickening agents include, but arenot limited to: cross-linked carboxypolymethylene polymers, ethylcellulose, polyethylene glycols, gum tragacanth, gum kharaya, xanthangums and bentonite, hydroxyethyl cellulose, and hydroxypropyl cellulose.

Creams can be formulated to contain a concentration effective to deliveran effective amount of therapeutic agent(s) of the invention to thetreated tissue, typically at between about 0.1%, preferably at greaterthan 1% up to and greater than 50%, preferably between about 3% and 50%,more preferably between about 5% and 15% therapeutic agent(s) of theinvention. The creams also contain from 5% to 50%, preferably from 10%to 25%, of an emollient and the remainder is water or other suitablenon-toxic carrier, such as an isotonic buffer. The emollients, asdescribed above for the lotions, can also be used in the creamcompositions. The cream may also contain a suitable emulsifier, asdescribed above. The emulsifier is included in the composition at alevel from 3% to 50%, preferably from 5% to 20%.

These compositions that are formulated as solutions or suspensions maybe applied to the skin, or, may be formulated as an aerosol or foam andapplied to the skin as a spray-on. The aerosol compositions typicallycontain [by weight] from 25% to 80%, preferably from 30% to 50%, of asuitable propellant. Examples of such propellants are the chlorinated,fluorinated and chlorofluorinated lower molecular weight hydrocarbons.Nitrous oxide, carbon dioxide, butane, and propane are also used aspropellant gases. These propellants are used as understood in the art ina quantity and under a pressure suitable to expel the contents of thecontainer.

Suitably prepared solutions and suspensions may also be topicallyapplied to the eyes and mucosa. Solutions, particularly those intendedfor ophthalmic use, may be formulated as 0.01%-10% isotonic solutions,pH about 5-7, with appropriate salts, and preferably containing one ormore of the compounds herein at a concentration of about 0.1%,preferably greater than 1%, up to 50% or more. Suitable ophthalmicsolutions are known [see, e.g., U.S. Pat. No. 5,116,868, which describestypical compositions of ophthalmic irrigation solutions and solutionsfor topical application]. Such solutions, which have a pH adjusted toabout 7.4, contain, for example, 90-100 mM sodium chloride, 4-6 mMdibasic potassium phosphate, 4-6 mM dibasic sodium phosphate, 8-12 mMsodium citrate, 0.5-1.5 mM magnesium chloride, 1.5-2.5 mM calciumchloride, 15-25 mM sodium acetate, 10-20 mM D.L.-sodium,.β.-hydroxybutyrate and 5-5.5 mM glucose.

Gel compositions can be formulated by simply admixing a suitablethickening agent to the previously described solution or suspensioncompositions. Examples of suitable thickening agents have beenpreviously described with respect to the lotions.

The gelled compositions contain an effective amount of therapeuticagent(s) of the invention, typically at a concentration of between about0.1-50% by weight or more of one or more of the compounds providedherein; from 5% to 75%, preferably from 10% to 50%, of an organicsolvent as previously described; from 0.5% to 20%, preferably from 1% to10% of the thickening agent; the balance being water or other aqueous ornon-aqueous carrier, such as, for example, an organic liquid, or amixture of carriers.

The formulations can be constructed and arranged to create steady stateplasma levels. Steady state plasma concentrations can be measured usingHPLC techniques, as are known to those of skill in the art. Steady stateis achieved when the rate of drug availability is equal to the rate ofdrug elimination from the circulation. In typical therapeutic settings,the therapeutic agent(s) of the invention will be administered topatients either on a periodic dosing regimen or with a constant infusionregimen. The concentration of drug in the plasma will tend to riseimmediately after the onset of administration and will tend to fall overtime as the drug is eliminated from the circulation by means ofdistribution into cells and tissues, by metabolism, or by excretion.Steady state will be obtained when the mean drug concentration remainsconstant over time. In the case of intermittent dosing, the pattern ofthe drug concentration cycle is repeated identically in each intervalbetween doses with the mean concentration remaining constant. In thecase of constant infusion, the mean drug concentration will remainconstant with very little oscillation. The achievement of steady stateis determined by means of measuring the concentration of drug in plasmaover at least one cycle of dosing such that one can verify that thecycle is being repeated identically from dose to dose. Typically, in anintermittent dosing regimen, maintenance of steady state can be verifiedby determining drug concentrations at the consecutive troughs of acycle, just prior to administration of another dose. In a constantinfusion regimen where oscillation in the concentration is low, steadystate can be verified by any two consecutive measurements of drugconcentration.

FIG. 8 shows a kit according to the invention. The kit 10 includes avial 12 containing an opioid tablet. The kit 10 also includes a vial 14containing R-MNTX tablets which contain pellets, some of which areenterically coated with pH sensitive material and some of which areconstructed and arranged to release the R-MNTX immediately in thestomach. The kit also includes instructions 20 for administering thetablets to a subject who is constipated or who has symptoms ofconstipation or gastrointestinal immotility. The instructions includeindicia, for example writing, indicating that the R-MNTX is pure R-MNTXfree of S-MNTX.

In some aspects of the invention, the kit 10 can include optimally oralternatively a pharmaceutical preparation vial 16, and a pharmaceuticalpreparation diluents vial 18. The vial containing the diluents for thepharmaceutical preparation is optional. The diluents vial containsdiluents such as physiological saline for diluting what could be aconcentrated solution or lyophilized powder of R-MNTX. The instructionscan include instructions for mixing a particular amount of the diluentswith a particular amount of the concentrated pharmaceutical preparation,whereby a final formulation for injection or infusion is prepared. Theinstructions 20 can include instructions for treating a patient with aneffective amount of R-MNTX. It also will be understood that thecontainers containing the preparations, whether the container is abottle, a vial with a septum, an ampoule with a septum, an infusion bag,and the like, can contain additional indicia such as conventionalmarkings which change color when the preparation has been autoclaved orotherwise sterilized.

This invention is not limited in its application to the details ofconstruction and the arrangement of components set forth in thefollowing description or illustrated in the drawings. The invention iscapable of other embodiments and of being practiced or of being carriedout in various ways. Also, the phraseology and terminology used hereinis for the purpose of description and should not be regarded aslimiting. The use of “including,” “comprising,” or “having,”“containing”, “involving”, and variations thereof herein, is meant toencompass the items listed thereafter and equivalents thereof as well asadditional items.

EXAMPLES Example 1 HPLC Analysis of R- and S-MNTX

HPLC analysis was performed on a Varian ProStar HPLC controlled byVarian Star software using the following method:

HPLC Method I:

-   Column: Luna C18(2), 150×4.6 mm, 5μ-   Flow Rate: 1 mL/min-   Detection: UV @ 230 nm-   Gradient Program:

Time (min) % A % B  0:00 95 5  8:00 65 35 12:00 35 65 15:00 0 100 16:0095 5 18:00 95 5 Mobile phase A = 0.1% Aqueous TFA Mobile phase B = 0.1%Methanolic TFA TFA = trifluoroacetic acidHPLC Method II:

-   Chromatographic Conditions and Parameters: Analytical Column    Description:-   Phenomenex Inertsil ODS-3 150×4.6 mm, 5 μm Column Temperature:    50.0° C. Flow-   Rate: 1.5 mL/min Injection Volume: 20 μL Detection Wavelength: 280    nm Mobile-   Phase: A=Water:MeOH:TFA (95:5:0.1%; v/v/v) B=Water:MeOH:TFA-   (35:65:0.1%; v/v/v) Analysis Time: 50 min-   Quantitation limit: 0.05%-   Detection limit: 0.02%-   Gradient Profile:

Time (min) % A % B Curve 0:00 100 0 Initial 45 50 50 Linear 48 100 0Linear 55 100 0 Hold Mobile Phase A (Water:MeOH:TFA::95:5:0.1%, v/v/v)Mobile Phase B (Water:MeOH:TFA::35:65:0.1%, v/v/v) MeOH = Methanol TFA =trifluoroacetic acid

The synthesis and purification of R-MNTX were monitored using the aboveHPLC protocol. S-MNTX is distinguished from R-MNTX using the HPLCconditions described. Authentic S-MNTX for use as a standard may be madeusing the protocol as described herein. In a typical HPLC run, S-MNTXelutes about 0.5 minutes before R-MNTX elutes. The retention time ofS-MNTX is approximately 9.3 minutes; the retention time of R-MNTX isabout 9.8 minutes.

As illustrated in FIG. 2, the S and R forms of MNTX can be distinguishedclearly on an HPLC chromatogram. FIG. 3 is an HPLC chromatogram of amixture of 0.1% by weight of authentic S form added to 99.5% by weightof authentic R form; FIG. 4 is a chromatogram of 1.0% by weight ofauthentic S form added to 99.0% by weight of authentic R form. FIG. 5 isa chromatogram of 3.0% by weight of authentic S form added to 98.0% byweight of authentic R form. This has permitted applicants to devise andtest for the first time stereoselective protocols for synthesis andpurification that yield highly pure R-MNTX from3-O-protected-naltrexone.

Example 2 Stereoselective Synthesis of R-MNTX

The synthetic scheme for Example 2 is shown in FIG. 6.

General. All anhydrous reactions were carried out in oven-dried (130°C.) glassware under an atmosphere of dry nitrogen (N₂). All commercialreagents and solvents were used without any additional purification.Nuclear magnetic resonance (NMR) spectra were obtained using either aVarian Gemini or Varian Mercury 300 MHz spectrometer. Mass spectra weredetermined on a Finnigan LCQ. HPLC purity was determined using a Waters717 Autosampler and Waters 996 Photodiode Array Detector.

3-O-Isobutyryl-Naltrexone (2). To a solution of compound (1) (1.62 g,4.75 mmol) in anhydrous tetrahydrofuran (THF) (120 mL) at 0° C. wasadded triethylamine (NEt3) (1.4 mL, 10 mmol). After the reaction wasstirred for 15 min. at 0° C., isobutyryl chloride (1.05 mL, 10 mmol) wasadded dropwise. Reaction mixture was stirred at 0° C. for 1 hr, then atroom temperature for 18 hr before being quenched with saturated sodiumbicarbonate (NaHCO₃) (aq) (70 mL) and 30 ml of H₂O. The reaction wasextracted with methylene chloride (CH₂Cl₂) (2×200 mL). The extracts werecombined, washed with brine (130 ml), dried over sodium sulfate (Na₂SO₄)(50 g), filtered and concentrated in vacuo. The crude material waspurified by flash chromatography on silica gel (column size 40×450 mm,silica gel was loaded 40×190 mm) (9.8:0.2→9.6:0.4→9.4:0.6 CH₂C₁₂/MeOH)to give compound (2) (1.5 g 76.8%) as a white solid.

¹H NMR (300M Hz, CDCl₃) δ 6.82 (d, J=8.0 Hz, 1H), 6.67 (d, J=8.0 Hz,1H), 4.69 (s, 1H), 3.21 (d, J=6.0 Hz, 1H), 3.12-2.96 (m, 2H), 2.93-2.82(m, 1H), 2.71 (dd, J=4.5 Hz, 1H), 2.62 (dd, J=6.2 Hz, 1H), 2.48-2.28 (m,4H), 2.19-2.10 (m, 1H), 1.93-1.86 (m, 1H), 1.68-1.59 (m, 2H), 1.34 (d,J=0.8 Hz, 3H, CH₃-isobutyryl), 1.31 (d, J=0.8 Hz, 3H, CH₃-isobutyryl),0.90-0.83 (m, 1H, CH-cyclopropyl), 0.60-0.54 (m, 2H, CH₂-cyclopropyl),0.18-0.13 (m, 2H, CH2-cyclopropyl). 13C NMR (75.5 MHz, CDCl₃) δ 207.6(CO), 174.7 (COO/Pr)147.8, 132.8, 130.1, 130.0, 122.8, 119.2, 90.5,70.0, 61.9, 59.2, 50.6, 43.4, 36.1, 33.8, 31.2, 30.7, 22.9, 19.0, 18.9,9.4, 4.0, 3.8. MS[M+H]⁺: 412.

3-O-Isobutyryl-N-Methylnaltrexone Iodide salt (3). Compound (2) (689 mg,1.67 mmol) was transferred by spatula into a glass pressure vessel. Thevessel was purged gently with nitrogen on the manifold for 5 minutes andwas then evacuated under high vacuum. When the vacuum was constant, thelower part of the vessel was immersed in liquid nitrogen. Methyl iodide(973 mg, 6.85 mmol) was dispensed into a separate flask on the manifoldinto a nitrogen atmosphere and frozen in liquid nitrogen. The frozenmethyl iodide vessel was evacuated under high vacuum. The main manifoldchamber was isolated from the high vacuum pump. The methyl iodide wasallowed to warm to ambient temperature and sublime via the main chamberonto the liquid nitrogen cooled 3-O-Isobutyryl-Naltrexone. Whensublimation was complete, nitrogen was slowly allowed to leach into theglass pressure vessel. The vessel was then sealed tight, removed fromthe manifold and heated in an oil bath at 88-90° C. for 17 hrs. Thevessel was allowed to cool to ambient temperature before allowingnitrogen to flow into the vessel. The vessel was then evacuated underhigh vacuum to remove residues of unreacted methyl iodide giving a whitesolid. A sample of the solid was removed for ¹H NMR analysis. Thisshowed good conversion to product. Thin layer chromatography (TLC) ofthe product [dichloromethane/methanol 9:1 (v/v), normal phase silica, UVdetection] showed a trace of starting material (2) (R_(f)=0.8) and adiffuse region (R_(f)=0-0.4). The solid was dissolved indichloromethane/methanol (4:1, minimum volume) and applied to a silicagel column (ultrapure silica gel, 22 g in dichloromethane, beddimensions: 200 mm×20 mm id). The column was eluted as follows:

-   Dichloromethane/methanol 98:2 (300 ml)-   Dichloromethane/methanol 97:3 (300 ml)-   Dichloromethane/methanol 94:6 (200 ml)-   Dichloromethane/methanol 92:8 (400 ml)    Fractions were analyzed by TLC [dichloromethane/methanol 9:1 (v/v),    normal phase silica, UV detection]. Fractions containing exclusively    the principal component (R_(f)=0.4) were combined rinsing together    with methanol, and concentrated to yield 867 mg of white solid. This    represents a 91% yield based on 3-O-Isobutyryl-Naltrexone. ¹H NMR is    consistent.

N-Methylnaltrexone Bromide/Iodide salt (4). Compound (3) (862 mg, 1.56mmol) was dissolved in methanol (13 ml). To this mixture was addedsterile water (11.5 ml) followed by 48% aqueous hydrobromic acid (1.5ml). The resultant mixture was stirred under nitrogen and heated in anoil bath at 64-65° C. for 6.5 hr. TLC analysis of a sample (dispersed inmethanol) of the reaction mixture showed no starting material (3)remaining (R_(f)=0.4) and conversion to material at R_(f)=0-0.15. Themixture was concentrated on the rotary evaporator with the bath at22-25° C. until approximately 1 ml of oily liquid remained. Acetonitrile(10 ml) was added and the mixture was reconcentrated. This was repeateda further three times, using 10 ml of acetonitrile, to give a gingercolored crisp foam (590 mg, 86% crude yield).

Preparation of Anion Exchange Resin Column. 30 g of AG 1-X8 resin waspacked into an medium pressure liquid chromatography (MPLC) column (20mm id) using 100 ml water to create a resin slurry. The resin bed waswashed with 1.0N aqueous hydrobromic acid (200 ml) and then sterilewater until the pH of the aqueous eluate was pH 6-7. Approximately 1.5 Lof water was required.

N-Methylnaltrexone Bromide (5). The foam (4) (597 mg) was dispersed inwater (6 ml)/methanol (2 ml). Some dark oil remained undissolved. Theclear supernatant liquid was decanted and applied to the prepared anionexchange resin column. The residue was washed twice with methanol (0.2ml)/water (3 ml). The supernatant liquors were applied to the column.The column was eluted with 4.2 L of sterile water and fractions of ˜20ml were collected. The presence of N-Methylnaltrexone salt was detectedby liquid chromatography/mass spectrometry (LC/MS). The majority ofN-Methylnaltrexone was located in the initial 1.5 L of eluate of whichthe first 600 ml contained the most pure material by TLC (4:1dichloromethane/methanol, normal phase silica). The first 600 ml ofeluate was combined and concentrated on the rotary evaporator to give awhitish glass. The water bath was maintained at ˜35° C. Care was neededto control foaming of the eluate while evaporating.

Purification of N-Methylnaltrexone Bromide (5). Recrystallization frommethanol. The residue was warmed in methanol (60 ml) under nitrogen tojust below reflux and then filtered through a glass sinter to remove asmall amount of insoluble material. This filtrate was then blown down ina stream of nitrogen to approximately 10 ml and then cooled undernitrogen in ice/water. Some white precipitate was formed but clearlymuch solid remained in solution. The mixture was then concentrated byevaporation to give a slightly colored gum. This was triturated withmethanol (3 ml×2). Methanol was cautiously decanted by pipette betweentriturations. The white residue was dissolved in methanol (60 ml) andfiltered through a glass sinter. The filtrate was concentrated toapproximately 1 ml and a further portion of methanol (1 ml) was added totriturate the solid. The supernatant liquors were decanted as before.The solid was dried to give a white solid, batch A (178.0 mg). HPLCanalysis showed 97.31% of R-MNTX, and 2.69% of S-MNTX.

All filtrates/supernatant liquors in methanol were combined andconcentrated to give a white glass. This residue was triturated withmethanol (3 ml×2) and the supernatant liquors were removed carefully asbefore. The residue was dissolved in methanol (50 ml) and filteredthrough a glass sinter. The filtrate was concentrated to approximately 1ml solution and a further portion of methanol (1 ml) was added totriturate the solid. The supernatant liquors were decanted as before andthe residue was triturated further with methanol (2 ml). The supernatantliquors were decanted and the residue was dried to give a white solid,batch B (266.0 mg). HPLC analysis of batch B showed 97.39% of R-MNTX,and 2.61% of S-MNTX. Batches A and B together represent a total yield of436.8 mg (64%). ¹H NMR is consistent. MS [M+H]⁺: 356.

As demonstrated in batches A and B, recrystallization from methanolyields product with high percentage of R-MNTX. In a reaction carried outunder the same conditions with ¹⁴CH₃-labelled material, it was foundthat the composition of the crude reaction mixture beforerecrystallization from methanol was 94.4% R-MNTX* and 4.7% S-MNTX*.Recrystallization from methanol yielded product containing 98.0% R-MNTX*and 1.5% S-MNTX*. A second recrystallization from methanol yielded 98.3%R-MNTX* and 1.2% S-MNTX*.

It should be understood that it is believed that the synthetic protocolresults in greater than 94% R form with only a small percentage of the Sform. Using synthesis Scheme 1, the substantially pure material, couldbe processed further on a chromatography column, preparative HPLC orrecrystallization. In one recrystallization following ion exchange, thepurity of the R form was greater than 98%. A second recrystallizationyielded 98.3% R-MNTX. It is understood that further recrystallizationsand/or chromatography, anywhere between one and four, (or even six or asmany as ten) times ensures greater than 99.95% R form and eliminatestraces of the S form, if present.

Example 3 Stereoselective Synthesis of R-MNTX

The synthetic scheme for Example 3 is shown in FIG. 7. In Example 3, themethod taught by Goldberg et al for protecting groups was followed.Acetyl, Goldberg et al's preferred protecting group, instead ofisobutyryl was used as the protecting group. The reactions were carriedout as described in Example 2. It was surprisingly found using thescheme shown in FIG. 7 that the acetyl protecting group tended to falloff during purification of intermediate 2 (O-acetyl-naltrexone). Thismade it difficult to obtain pure intermediate 2. The yield ofintermediate 2 with the acetyl group was only 36.3% rendering the schemeshown in FIG. 7 unsuitable for commercial scale-up. In contrast usingthe synthetic scheme with isobutyryl as the protecting group (FIG. 6),intermediate 2 (3-O-isobutyryl-naltrexone) was quite stable duringpurification resulting in a yield of 76.8%.

Example 4 Manufacturing Process for a Pharmaceutical Formulation ofR-MNTX

A manufacturing process can be outlined as follows:

-   -   1. Add required amount of water for injection (˜80% or final        volume) to a stainless steel tank.    -   2. Add chelating agent to the tank and stir till dissolved.    -   3. Add buffering agent to the tank and stir till dissolved.    -   4. Add R-MNTX to the tank and stir till dissolved.    -   5. Add isotonicity agent to the tank and stir till dissolved.    -   6. Adjust the pH of the solution to pH 3.25.    -   7. Add water for injection to increase the volume to the        required amount.    -   8. Transfer material to supply pressure vessel.    -   9. Sterile filter into a sterile stainless steel pressure        vessel.    -   10. Fill into bottles/vials, purge with nitrogen and then        stopper the bottles/vials.    -   11. Sterilize the filled vials by autoclaving.

Exact amount of excipients to be used:

Disodium edetate=0.75 mg/ml Added in step 2

Sodium citrate=0.199 mg/ml Added in step 3

Citric acid=0.35 mg/ml Added in step 3

Sodium chloride=8.5 mg/ml Added in step 5

The order of addition of excipients is described above. Steps 2 to 5 cantake place in any order.

When all excipients and drug have been added, step 6, pH of the solutionis adjusted by addition of acid. If a buffering agent is used in thesolution, pH adjustment may not be required.

There are no specifics on the temperature or the stirring speed duringthe formulation. The temperature during formulation can be as high as80° C.

Example 5 Preferred Manufacturing Process for a PharmaceuticalFormulation of R-MNTX

A preferred manufacturing process for 100 ml of 20 mg/ml solution ofR-MNTX solution is as follows:

-   1. Add 80 ml of water for injection (˜80% or final volume) to a    stainless steel tank.-   2. Add 75 mg of disodium edetate, a chelating agent, to the tank and    stir till dissolved.-   3. Add 19.9 mg of sodium citrate and 35 mg of citric acid (as    buffering agents) to the tank and stir till dissolved.-   4. Add 2000 mg of R-MNTX to the tank and stir till dissolved.-   5. Add 850 mg of sodium chloride, an isotonicity agent, to the tank    and stir till dissolved.-   6. Adjust the pH of the solution if necessary.-   7. Add water for injection to increase the volume to 100 ml.-   8. Transfer the material to supply pressure vessel.-   9. Sterile filter using a 0.22 micron filter into a sterile    stainless steel pressure vessel.-   10. Fill, purge with nitrogen and then stopper the bottles/vials.-   11. Sterilize the filled vials by autoclaving.

Example 6 Preparation of a Subcutaneous Formulation of R-MNTX

A formula for a low citrate/EDTA formulation is listed below:

Ingredient mg/mL R-MNTX 30 mg Sodium chloride 4 mg Citric acid 0.0875 mgTrisodium citrate 0.0496 mg Disodium edetate 0.75 mg Water for injectionq.s. to 1 gThe pH of this solution is 3.5 and can withstand an autoclaving process.

Example 7 Manufacturing Process for a Lyophilized PharmaceuticalFormulation of R-MNTX

The lyophilization cycle is used for the preparation of lyophilizedpreparation of R-MNTX. Forty milligrams of R-MNTX is mixed with 32 mg ofthe cryoprotecting agent, mannitol and q.s. to 1 mL using water forinjection.

-   1. Load chamber at room temperature (20-25° C.)-   2. Lower shelf temp to −45 degrees C. at 1.0 degrees C./min-   3. Hold shelf temp at −45 for 120 minutes-   4. When condenser is below −50 degrees C., evacuate the chamber to    100-125 mt.-   5. Ramp shelf to −20 degrees C. at 0.5 degrees C./min.-   6. Hold at −20 degrees C. for 16 hours-   7. Ramp shelf to +27 degrees C. at 0.10 degrees C./min.-   8. Hold for a minimum of 8 hours. Maintain chamber pressure at    100-125 mt for the entire cycle.-   9. Restore chamber to 11.0 PSIA + or −1.0 with sterile filtered    Nitrogen and then seat the closures (2″ Hg), then bleed to    atmospheric pressure with N₂ to unload. The pH of the solution after    lyophilization and reconstitution is 5.0.

The disclosures of all patents, patent applications and scientificpublications cited or referenced herein are incorporated by reference intheir entirety, including the co-pending U.S. patent application Ser.No. 11/441,452, titled: “(S)-N-METHYLNALTREXONE”, filed on May 25, 2006.In case of conflict between documents incorporated by reference and theinstant application, the instant application will control.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated various alterations, modifications,and improvements will readily occur to those skilled in the art. Suchalterations, modifications, and improvements are intended to be part ofthis disclosure, and are intended to be within the spirit and scope ofthe invention. Accordingly, the foregoing description and drawings areby way of example only.

1. A method for stereoselective synthesis comprising: methylating a compound of formula A:

to yield a compound of formula B:

wherein R is a hydroxyl protecting group selected from isobutyryl, 2-methyl butyryl, tertbutyl carbonyl, or R, taken together with the oxygen atom to which it is attached, is a silyl ether, a 2-tetrahydropyranyl ether, or an alkyl carbonate; and X⁻ is a counterion, wherein the compound is in the (R) configuration with respect to the nitrogen.
 2. The method of claim 1, wherein a methylating agent is used to methylate the compound of formula A.
 3. The method of claim 2, wherein the methylating agent comprises a methyl group susceptible to nucleophilic attack, and a leaving group.
 4. The method of claim 3, wherein the methylating agent is selected from the group consisting of methyl halide, dimethyl sulfate, methyl nitrate and methyl sulfonate.
 5. The method of claim 1, wherein the X⁻ counterion is an anion.
 6. The method of claim 5, wherein the anion is halide, phosphate, nitrate, or organic anionic-charged species.
 7. The method of claim 6, wherein the anion is a halide.
 8. The method of claim 7, wherein the halide is bromide, iodide, or chloride.
 9. The method of claim 6, wherein the organic anionic-charged species is sulfonate or carboxylate.
 10. The method of claim 9, wherein the sulfonate is mesylate, besylate, tosylate, or triflate.
 11. The method of claim 9, wherein the carboxylate is formate, acetate, citrate, or fumarate.
 12. The method of claim 1, further comprising removing the hydroxyl protecting group to form an (R)—N-methylnaltrexone salt.
 13. The method of claim 12, further comprising purifying the (R)—N-methylnaltrexone salt by chromatography or recrystallization, or a combination thereof.
 14. The method of claim 13, wherein the purifying is by reverse phase chromatography.
 15. The method of claim 13, wherein the purifying is by chromatography using alumina or silica gel.
 16. The method of claim 13, wherein the purifying is by recrystallization from methanol.
 17. The method of claim 13, wherein the (R)—N-methylnaltrexone salt after purification has chemical purity of greater than 98%.
 18. The method of any of claims 1 or 12, further comprising exchanging the X⁻ counterion with a different counterion.
 19. The method of claim 12, wherein the (R)—N-methylnaltrexone salt is (R)—N-methylnaltrexone iodide and the method further comprises the step of treating the (R)—N-methylnaltrexone iodide with an anion exchange material to yield (R)—N-methylnaltrexone bromide.
 20. The method of claim 1, wherein the compound of formula A:

is methylated to yield an (R)—N-methylnaltrexone iodide salt, the (R)—N-methylnaltrexone iodide salt is treated with hydrobromic acid to yield a bromide/iodide (R)—N-methylnaltrexone salt mixture, and the (R)—N-methylnaltrexone bromide/iodide salt is treated with an anion exchange material to yield (R)—N-methylnaltrexone bromide salt.
 21. The method of claim 1, further comprising purifying the compound of formula B:

by chromatography or recrystallization, or a combination thereof.
 22. The method of claim 21, wherein the purifying is by reverse phase chromatography.
 23. The method of claim 21, wherein the purifying is by chromatography using alumina or silica gel.
 24. The method of claim 21, wherein the purifying is by recrystallization from methanol. 